bluuebunny/crossref_metadata_2025 huggingface dataset:
Instantaneous measurement of left and right ventricular stroke volume and pressure-volume relationships with an impedance catheter.
Authors: McKay R G , Spears J R , Aroesty J M , Baim D S , Royal H D , Heller G V , Lincoln W , Salo R W , Braunwald E , Grossman W
Published: June 2011

The feasibility of using continuous on-line recording of intraventricular electrical impedance to measure ventricular stroke volume was assessed in 12 patients at cardiac catheterization with a multielectrode impedance catheter and a 1.3 kHz measuring current of 4 microA. Stroke volumes determined by electrical impedance were compared with stroke volumes determined by the thermodilution technique in 10 patients and correlated with an r value of .95. Directional changes in impedance recordings throughout the cardiac cycle were also compared with volume curves obtained from six patients by radionuclide ventriculography, and in all instances the agreement between the two volume recordings was excellent. For all patients, on-line measurements of impedance showed a beat-by-beat decrease in stroke volume with the Valsalva maneuver and the administration of amyl nitrite, as well as an immediate increase in stroke volume in the contraction following an extra-systolic beat. Similar directional changes in stroke volume were recorded in both left and right ventricles. Left ventricular pressure-volume relationships were assessed with simultaneous left ventricular pressure recordings and volume signals recorded from the impedance catheter to determine if impedance measurements of volume can be used clinically. Pressure-volume diagrams were subsequently plotted, and for all patients these diagrams showed characteristic isovolumetric contraction and relaxation phases as well as typical ejection and filling periods. Moreover, beat-by-beat sequential pressure-volume diagrams constructed for patients during the administration of amyl nitrite revealed a linear end-systolic pressure-volume relationship.(ABSTRACT TRUNCATED AT 250 WORDS)
Nifedipine and conventional therapy for unstable angina pectoris: a randomized, double-blind comparison.
Authors: Muller J E , Turi Z G , Pearle D L , Schneider J F , Serfas D H , Morrison J , Stone P H , Rude R E , Rosner B , Sobel B E
Published: June 2011

To characterize the potential of nifedipine in the therapy of unstable angina pectoris we implemented a blinded, randomly assigned, titrated schedule of conventional therapy (propranolol, if not contraindicated, and isosorbide dinitrate) or nifedipine for 14 days in 126 patients hospitalized in a coronary care unit for ischemic chest pain of less than 45 min duration. There were no significant differences between conventionally and nifedipine-treated patients with regard to (1) the time to relief of pain as judged by life table analysis, (2) the decrease in anginal attacks per 24 hr from day 0 to day 2 (-2.5 +/- 0.4 for conventional therapy vs; -2.8 +/- 0.3 for nifedipine), (3) the decrease in the number of nitroglycerin tablets consumed per 24 hr (-2.0 +/- 0.5 for conventional vs -2.1 +/- 0.4 for nifedipine therapy), (4) the percentage of patients requiring morphine on day 1 (13% for conventional vs 21% for nifedipine therapy), or (5) the percentage of patients who developed infarction (14% in both groups). Among the 27 patients who did not respond to initial conventional (n = 13) or nifedipine therapy (n = 14), five in each group became pain free when the opposite therapy (either nifedipine or conventional therapy) was added. In the subgroup of 67 patients who were receiving propranolol before randomization, addition of nifedipine was more effective in controlling pain than was an increase in conventional therapy (p = .026). In the subgroup of 59 patients not receiving prior propranolol, initiation of conventional therapy produced more rapid pain relief than initiation of nifedipine therapy alone (p less than .001), which tended to increase heart rate. Thus, for the study population as a whole therapy with nifedipine alone was equivalent to conventional therapy for unstable angina, although this overall equivalence may result from a combination of superiority of nifedipine therapy in patients previously receiving beta-blocker therapy and superiority of beta-blocker therapy in patients not previously receiving beta-blockers.
Autonomic mechanisms in ventricular fibrillation induced by myocardial ischemia during exercise in dogs with healed myocardial infarction. An experimental preparation for sudden cardiac death.
Authors: Schwartz P J , Billman G E , Stone H L
Published: June 2011

The relationship between activity of the autonomic nervous system, myocardial ischemia, and malignant arrhythmias has been investigated in a new experimental preparation for sudden death. Fifty-seven dogs were chronically instrumented and studied under control conditions (n = 15) and 1 month after production of an anterior myocardial infarction (n = 42). The protocol consisted in occluding the left circumflex coronary artery for 2 min, commencing at the last minute of an exercise stress test and extending through the first minute after cessation of exercise. With this protocol, ventricular fibrillation was observed in 40% of normal dogs and 66% of dogs with infarction. In 14 dogs with infarction, left stellectomy reduced the incidence of ventricular fibrillation to zero (p less than .001). The reflex changes in heart rate elicited within the first minute of ischemia during exercise in the animals that survived (from 204 +/- 14 to 198 +/- 31 beats/min, -6) were opposite those in animals that had ventricular fibrillation (from 208 +/- 24 to 229 +/- 30 beats/min, +21) (p less than .05). The ischemia-induced reduction in heart rate despite continuation of exercise suggests the presence in the dogs that survived of active vagal reflexes that may have played an important role in the maintenance of cardiac electrical stability. This preparation has the potential to induce ventricular fibrillation consistently in conscious animals by the interaction of a few clinically relevant factors (acute myocardial ischemia, submaximal exercise and its cessation, sympathetic and vagal reflexes, and heart rate) and offers the possibility of acquiring further insights into the mechanisms of malignant arrhythmias and evaluating novel strategies for targeted prevention.
Effects of a calcium-entry blocker (diltiazem) on regional myocardial flow and function during exercise in conscious dogs.
Authors: Matsuzaki M , Gallagher K P , Patritti J , Tajimi T , Kemper W S , White F C , Ross J
Published: June 2011

We examined the effects of diltiazem, a calcium-entry blocker, on exercise-induced myocardial ischemia in nine conscious dogs with chronic coronary stenoses. An ameroid constrictor, Doppler flow probe, and hydraulic occluder were placed around the left circumflex coronary artery, and left ventricular pressure was measured (Konigsberg micromanometer). Pairs of ultrasonic crystals were implanted for measuring left ventricular systolic wall thickening (% delta WTh) in control (left ventricular anterior wall) and ischemic (left ventricular posterior wall) regions, and regional myocardial blood flow was measured with the microsphere method. Eighteen days (average) after surgery mean coronary blood flow velocity had decreased and reactive hyperemic flow velocity after 10 sec of coronary occlusion was markedly reduced, but % delta WTh at rest remained normal, indicating collateral development. Control treadmill exercise was performed for 3.7 min (average), and 2 hr later administration of 0.3 mg/kg diltiazem was followed by an identical exercise bout. Control exercise increased % delta WTh in the normal region, while in the ischemic region % delta WTh decreased markedly and ischemia was evident (subendocardial flow, 0.29 +/- 0.12[SD] ml/min/g). After diltiazem hemodynamic and % delta WTh values at rest were not changed; during exercise the heart rate was significantly lower (204 +/- 24 vs 227 +/- 33 beats/min, p less than .01), but values for other hemodynamic measures were similar to those during the control run. % delta WTh in the control region was not changed during exercise after diltiazem, but compared with control exercise in the ischemic zone there was less dysfunction and subendocardial flow was greater. Recovery from exercise-induced dysfunction in the ischemic region occurred within 5 min, compared with over 30 min after control exercise. Thus, in a preparation of chronic coronary stenosis, the calcium-entry blocker improved the relationship between regional myocardial flow and function during exercise and led to more rapid recovery of regional myocardial dysfunction.
Mechanisms by which epinephrine augments cerebral and myocardial perfusion during cardiopulmonary resuscitation in dogs.
Authors: Michael J R , Guerci A D , Koehler R C , Shi A Y , Tsitlik J , Chandra N , Niedermeyer E , Rogers M C , Traystman R J , Weisfeldt M L
Published: June 2011

The goals of this study were to quantify the effects of epinephrine on myocardial and cerebral blood flow during conventional cardiopulmonary resuscitation (CPR) and CPR with simultaneous chest compression-ventilation and to test the hypothesis that epinephrine would improve myocardial and cerebral blood flow by preventing collapse of intrathoracic arteries and by vasoconstricting other vascular beds, thereby increasing perfusion pressures. Cerebral and myocardial blood flow were measured by the radiolabeled microsphere technique, which we have previously validated during CPR. We studied the effect of epinephrine on established arterial collapse during CPR with simultaneous chest compression-ventilation with the abdomen bound or unbound. Epinephrine reversed arterial collapse, thereby eliminating the systolic gradient between aortic and carotid pressures and increasing cerebral perfusion pressure and cerebral blood flow while decreasing blood flow to other cephalic tissues. Epinephrine produced higher cerebral and myocardial perfusion pressures during CPR with simultaneous chest compression-ventilation when the abdomen was unbound rather than bound because abdominal binding increased intracranial and venous pressures. In other experiments we compared the effect of epinephrine on blood flow during 1 hr of either conventional CPR or with simultaneous chest compression-ventilation with the abdomen unbound. Epinephrine infusion during conventional CPR produced an average cerebral blood flow of 15 ml/min . 100 g (41 +/- 15% of control) and an average myocardial blood flow of 18 ml/min . 100 g (15 +/- 8% of control). In our previous studies, cerebral and myocardial blood flow were less than 3 +/- 1% of control during conventional CPR without epinephrine. Although flows during CPR with simultaneous chest compression-ventilation without epinephrine were initially higher than those during conventional CPR, arterial collapse developed after 20 min, limiting cerebral and myocardial blood flow. The use of epinephrine throughout 50 min of CPR with simultaneous chest compression-ventilation maintained cerebral blood flow at 22 +/- 2 ml/min . 100 g (73 +/- 25% control) and left ventricular blood flow at 38 +/- 9 ml/min . 100 g (28 +/- 8% control). The improved blood flows with epinephrine correlated with improved electroencephalographic activity and restoration of spontaneous circulation.(ABSTRACT TRUNCATED AT 400 WORDS)
Diastolic stiffness and myocardial structure in aortic valve disease before and after valve replacement.
Authors: Hess O M , Ritter M , Schneider J , Grimm J , Turina M , Krayenbuehl H P
Published: June 2011

Passive diastolic properties were determined in 10 control patients and 21 patients with aortic valve disease before and 17.5 months after successful valve replacement. Ten patients had severe aortic stenoses (AS), five had combined aortic valve lesions (AS + aortic insufficiency [AI]), and six patients had severe AI. Left ventricular endomyocardial biopsies were obtained before and after surgery in patients with AS, AS + AI, and AI. Simultaneous echocardiographic and high-fidelity pressure measurements were made in all patients, and left ventricular chamber stiffness was calculated from a viscoelastic pressure-circumference relationship and left ventricular myocardial stiffness from a viscoelastic stress-strain relationship. The constant of chamber stiffness, beta', was slightly although not significantly increased in patients with AS (0.27 before and 0.24 after surgery), but was normal in those with AS + AI (0.22 before and 0.17 after surgery) and slightly decreased in those with AI (0.18 before and 0.16 after surgery) when compared with in control subjects (0.21). The constant of myocardial stiffness beta was normal in patients with AS (13.2), AS + AI (11.5), and AI (11.7) before surgery compared with in the control group (12.5). beta increased, however, significantly in those with AS (25.2; p less than .02), but not in those with AS + AI (16.3; NS) and AI (12.8; NS) after surgery. Myocardial morphologic characteristics showed a significant decrease in muscle fiber diameter in patients with AS, AS + AI, and AI, as well as a significant increase in interstitial fibrosis from 15% to 26% (p less than .05) in those with AS and a slight increase from 15% to 22% (NS) in those with AS + AI and from 19% to 24% (NS) in those with AI. Left ventricular fibrous content (left ventricular muscle mass index multiplied by interstitial fibrosis) remained, however, unchanged in all three groups after aortic valve replacement. In conclusion, left ventricular chamber stiffness is increased in AS but decreased in AI, whereas LV myocardial stiffness is normal in patients with aortic valve disease before surgery. After surgery, left ventricular myocardial stiffness increased significantly in AS patients but remained unchanged in those with AI. Postoperative changes in myocardial structure were characterized by a decrease in muscle fiber diameter and a relative increase in interstitial fibrosis, whereas fibrous content remained unchanged. Thus, regression of myocardial hypertrophy in aortic valve disease is accompanied by an increase of myocardial stiffness in concentric hypertrophy that is not seen in eccentric hypertrophy.
Influence of persistent obesity in children on cardiovascular risk factors: the Bogalusa Heart Study.
Authors: Aristimuño G G , Foster T A , Voors A W , Srinivasan S R , Berenson G S
Published: June 2011

The relationship between body fat indexes, lipid and lipoprotein levels, and blood pressure was studied in 2230 children, each examined during 1973, 1976, and 1978. The children were grouped with the use of seven percentile (P) intervals of triceps skinfold thickness that were specific for race, sex, and age; cardiovascular risk factor variables were assessed over time. Of the 238 children initially in the lowest P group (less than 15P), 44% remained there, and 65% had skinfold thicknesses below 30P on the three occasions. Of the 352 children in the highest P group (greater than or equal to 85P), who were considered to be very obese, 39% remained at this level while 69% remained at 70P or greater. Of the 366 considered to be obese (greater than or equal to 70, less than 85%P), 38% remained at or above 70P. At baseline, children in the seven groups differed in weight, ponderosity (wt/ht3), systolic and diastolic blood pressures, serum triglyceride levels, and pre-beta- and beta-lipoprotein cholesterol levels. Pairwise comparison of data from children in each of the six other groups with those from children in the middle range (greater than or equal to 40, less than 60P) showed that the obese and very obese children had significantly higher systolic blood pressures (p less than .05), while only those in the highest P group had significantly greater diastolic blood pressures (p less than .05). These differences increased and diverged over time. Those in the obese and very obese groups showed a striking drop over time in alpha-lipoprotein cholesterol levels and increases in pre-beta-lipoprotein cholesterol levels and systolic blood pressure. Triglyceride levels decreased over time for the lowest and middle range groups but remained at higher levels in obese and very obese children. There was a strong tendency for tracking (remaining in the same P group over time) in lean, obese, and very obese children. Those who tracked showed definite differences in risk factor variables at the baseline level and over time when compared with the middle range group. Since consistent obesity in early life enhances cardiovascular risk, the measurement over time of skinfold thickness in children is a useful method to detect the potential for adult cardiovascular disease.
Improved neurologic recovery and survival after early defibrillation.
Authors: Weaver W D , Copass M K , Bufi D , Ray R , Hallstrom A P , Cobb L A
Published: June 2011

Eighty-seven patients who had out-of-hospital cardiac arrests received defibrillating shocks delivered by minimally trained first responders before the arrival of paramedics in a city with short emergency response times. Their outcomes were compared with those of 370 other victims who received only basic life support by first responders until paramedics arrived. Survival was improved by early defibrillation in cases in which there was a delay in initiating cardiopulmonary resuscitation and in which paramedic response times exceeded 9 min; there was 62% survival after early defibrillation by first responders and 27% if first responders provided only basic life support (p less than .02). Neurologic recovery was also improved after early defibrillation. Eighteen of 46 resuscitated patients (39%) receiving early defibrillation were awake at 24 hr compared with 49 of 204 patients (24%) who received only basic life support while awaiting paramedics (p less than .02). Incorporating defibrillation as part of basic life support can reduce both mortality and morbidity from cardiac arrest, even in cities with established, rapidly responding emergency care systems.
Validation of a Doppler echocardiographic method for calculating severity of discrete stenotic obstructions in a canine preparation with a pulmonary arterial band.
Authors: Valdes-Cruz L M , Horowitz S , Sahn D J , Larson D , Oliveira Lima C , Mesel E
Published: June 2011

The purpose of this study was to develop an open-chest animal preparation to validate the accuracy of a two-dimensional Doppler echocardiographic method for estimating pressure drops across discrete stenotic obstructions. Six mongrel dogs underwent median sternotomy and catheters were placed in the right ventricle, distal main pulmonary artery, and aorta of each. A 1/8 inch umbilical tape was sewn to the posterior rim of the pulmonary artery just above the anulus and was progressively tightened to vary the degree of stenosis. Ultrasound and Doppler studies were performed with a 2.5 MHz phased-array unit with capabilities for pulsed or continuous-mode Doppler and real-time imaging. Peak systolic main pulmonary arterial flow velocities were recorded by Doppler echocardiography within the jet distal to the band from an oblique parasternal short-axis echocardiographic view and corrected for angle of incidence between the direction of Doppler sampling and the presumed direction of flow. Doppler velocities were converted to gradients with a simplification of the Bernoulli equation (gradient = 4 X maximal Doppler flow velocity2 ). Maximal Doppler-determined systolic pulmonary arterial velocities showed a good linear correlation with the 63 measured pressure drops (r = .95, SEE +/- 36.3 cm/sec). An excellent correlation was also found between Doppler-calculated and actual pressure gradients (r = .96, SEE +/- 7.26 mm Hg). Our results suggest that this Doppler method for measuring gradients across discrete stenotic obstructions may be quite accurate in clinical applications.
The effects of daily exercise on susceptibility to sudden cardiac death.
Authors: Billman G E , Schwartz P J , Stone H L
Published: June 2011

The purpose of this study was to investigate the effects of daily exercise on susceptibility to sudden cardiac death. A 2 min coronary occlusion was initiated during the last minute of an exercise stress test and continued for 1 min after cessation of exercise in chronically instrumented dogs with a healed anterior wall myocardial infarction. Thirteen dogs developed ventricular fibrillation (VF; susceptible), while five did not (resistant). Before the exercise plus ischemia test, the baroreflex was evaluated with a bolus injection of phenylephrine (10 micrograms/kg). The changes in heart rate caused by a 30 mm Hg increase in systolic arterial pressure as well as the slopes of either heart rate or RR interval plotted against systolic arterial pressure were significantly lower in dogs that developed VR (resistant, -49.6 +/- 7.8; susceptible, -15.3 +/- 6.4 beats/min; p less than .001). Four resistant and eight susceptible animals were then placed on a 6 week daily exercise program, while eight susceptible dogs had an equal period of rest. At the end of the 6 week period the exercise plus ischemia test was repeated; no susceptible animal that performed daily exercise developed VF, and all but one of the rested animals did. Daily exercise improved baroreflex control of heart rate in the susceptible group but not in the resistant group. Rest did not alter baroreflex function (change in heart rate after 30 mm Hg increase in systolic arterial pressure: after 6 weeks of exercise, resistant -43.3 +/- 18.9 beats/min, susceptible -60.8 +/- 16.6 beats/min; after 6 weeks of rest, susceptible 27.4 +/- 11.0 beats/min). We conclude that daily exercise prevents VF induced by acute myocardial ischemia in a subpopulation of dogs that were previously identified as susceptible to sudden cardiac death. Exercise also altered the autonomic control of the heart, possibly decreasing sympathetic and/or increasing parasympathetic tone.(ABSTRACT TRUNCATED AT 250 WORDS)
A comparison of quantitative echocardiographic methods for delineating infarct-induced abnormal wall motion.
Authors: Gillam L D , Hogan R D , Foale R A , Franklin T D , Newell J B , Guyer D E , Weyman A E
Published: June 2011

Current echocardiographic methods for quantitating abnormal regional left ventricular wall motion rely primarily on changes in endocardial excusion from end-diastole to end-systole. Recent studies demonstrating important spatial and temporal heterogeneity in wall motion within ischemic regions, however, raise questions about the validity of this approach. To determine the optimal method for defining abnormal left ventricular wall motion, we used a canine preparation of acute experimental infarction to examine four quantitative methods of wall motion analysis. The circumferential extent of abnormal wall motion assessed by each method was compared with the circumferential extent of infarction (defined by triphenyltetrazolium chloride staining) and the circumferential extent of reduced transmural blood flow (determined by radiolabeled microsphere techniques) 6 hr after acute coronary occlusion. The following methods of quantitating abnormal wall motion were examined: (1) determination of end-diastolic to end-systolic endocardial excursion (less than 0.20 end-diastolic radius), (2) determination of the extent of maximal dyskinesis (systolic bulging), and (3) and (4) two derived correlation methods that consider the entire course of systolic radial motion by correlating the observed echocardiographic field-by-field (every 16.7 msec) motion of each of 36 evenly spaced endocardial targets with the course of normal motion established from pooled normal data. Results obtained with the correlation methods showed a better correlation with the triphenyltetrazolium chloride-defined circumferential extent of infarction (r = .87 and r = .78) than did determinations of reduced end-diastolic to end-systolic endocardial excursion (r = .35) or the extent of maximal dyskinesis (r = .37). Similarly, the best correlation with the extent of reduced flow was obtained with one of the correlation methods (r = .80). We conclude that correlation methods that "integrate" endocardial motion over the entire systolic contraction sequence provide better definition of ischemic left ventricular dysfunction than do methods that consider motion at only single points in time.
Programmed electrical stimulation in patients with high-grade ventricular ectopy: electrophysiologic findings and prognosis for survival.
Authors: Gomes J A , Hariman R I , Kang P S , El-Sherif N , Chowdhry I , Lyons J
Published: June 2011

The significance and treatment of ventricular premature beats (VPBs) in patients without sustained ventricular tachycardia (VT), sudden death, or syncope remains unclear. We undertook a prospective study of programmed electrical stimulation (up to two extrastimuli and burst pacing) in 73 patients (age 60 +/- 10 years) with high-grade VPBs who had no evidence of sustained VT, sudden death, or syncope as determined by 48 hr of monitoring in the cardiac care unit and 48 hr Holter monitoring. Fifty-six patients (76.7%) had atherosclerotic heart disease, 10 (13.7%) had cardiomyopathy or valvular heart disease, and seven (9.6%) had no evident heart disease. Thirty-seven patients (50.7%) had Lown grade IVB VPBs, 30 (41.1%) had Lown grade IVA VPBs, and six (8.2%) had Lown grade III VPBs. Programmed electrical stimulation identified two groups of subjects: group 1 comprised 20 patients (27%) in whom VT or ventricular fibrillation was induced, group 2 comprised 53 patients (73%) in whom no ventricular arrhythmia or only two to four repetitive ventricular responses were induced. There was a significant difference between the presence of atherosclerotic heart disease, old myocardial infarction, and ejection fraction of less than 40% in group 1 compared with group 2. However, there was no significant difference in the grade of VPBs between the two groups. Seventeen of 20 patients from group 1 were placed on antiarrhythmic therapy (defined by programmed electrical stimulation), whereas group 2 patients were randomly assigned to prophylactic antiarrhythmic therapy. A total of 70 patients were followed up for 30 +/- 15 months. The incidence of sustained VT and/or sudden death (31.5% vs 2%; p less than .001) was significantly higher in group 1 compared with group 2.(ABSTRACT TRUNCATED AT 250 WORDS)
Multivariate analysis of angiographic, histologic, and electrocardiographic data in patients with coronary heart disease.
Authors: Flameng W , Wouters L , Sergeant P , Lewi P , Borgers M , Thone F , Suy R
Published: June 2011

In 61 consecutive patients undergoing aortocoronary bypass grafting, angiographic and electrocardiographic (ECG) changes were studied. Histologic delineation of myocardium was obtained by analysis of transmural biopsy specimens acquired at the time of surgery. The use of principal-component analysis revealed three definite groups of patients. Group I comprised patients with histologic findings associated with severe left anterior descending coronary artery (LAD) stenosis, without abnormal wall motion or ejection fraction. ECG abnormalities were limited to ST changes. Group II comprised patients with severe myocardial cell degeneration with only modest fibrosis associated with severe LAD stenosis and severely impaired wall motion. The incidence of infarction on the ECG was low. Group III patients had important myocardial cell degeneration with severe fibrosis associated with severe LAD stenosis, severely depressed wall motion, and significantly impaired ejection fraction. In this group there was a high incidence of infarction apparent on the ECG. Postoperative follow-up (24 months) showed a total survival of 94.4% in group I, 92.8% in group II, and only 72.7% in group III. This identification of subtypes of coronary artery disease seems to be helpful in estimating patient prognosis after coronary surgery.
The effects of familial relationships, age, body weight, and diet on blood pressure and the 24 hour urinary excretion of sodium, potassium, and creatinine in men, women, and children of randomly selected families.
Authors: Connor S L , Connor W E , Henry H , Sexton G , Keenan E J
Published: June 2011

Two hundred thirty-three randomly selected families provided a population for studying the effects of familial relationships, age, diet, body weight, and urinary electrolyte excretion on blood pressure. There was a strong familial component for urinary sodium, potassium, and creatinine excretion and for systolic blood pressure. In individuals, age, heart rate, and body weight were independently related to blood pressure. In women, urinary sodium and potassium levels were related to diastolic blood pressure. These individual relationships persisted when age was accounted for but were no longer significant after adjusting for both age and body weight, suggesting that heavier people eat more food, which in our culture means greater sodium intake. In fact, our randomly selected families were eating as much sodium (130 to 170 meq/day) and as little potassium (50 to 70 meq/day) as consumed by Americans several decades ago. Furthermore, this study again documented the rise in blood pressure with age, which may represent the effect of environmental influences on blood pressure over time. The familial aggregation of urinary sodium, potassium, and creatinine excretion, along with the well-established familial aggregation of body weight, emphasizes the importance of the entire family in the treatment and prevention of hypertension.
Coronary angiographic examination with the dynamic spatial reconstructor.
Authors: Block M , Bove A A , Ritman E L
Published: June 2011

The dynamic spatial reconstructor (DSR), a high temporal resolution, three-dimensional roentgenographic, computed tomography scanner, was used to scan the coronary arteries of five dogs. After one injection of contrast medium into the left main coronary artery or into the aortic root of each dog, all major epicardial coronary arteries and the septal artery could be imaged. After selective removal of all nonangiographically enhanced anatomical structures within the three-dimensional images, pseudo three-dimensional displays were generated to show the arteries from all possible views--even the strictly cranial view--so that superposition of arteries could be avoided. The geometric accuracy of the images was evaluated by comparing coronary arterial segment length measured by the DSR with postmortem measurements (r = .99, SEE = 3.12 mm, n = 35) and by measuring the stenosis produced by nine hollow plastic cylinders lodged in coronary arterial lumina via percutaneous catheterization. Three of the plugs had irregular noncircular lumina drilled into them so that the percentage of stenosis seen in some projection images underestimated the severity of stenosis. The DSR overestimated the length of a 3 mm long stenosis by 0.4 +/- 0.5 mm. The percent area reduction caused by the hollow cylinders varied between 53% and 92% and was underestimated by the DSR on the average by 7%. The correlation between DSR measurements and the direct measurements was r = .85 (SEE = 5%, n = 9). The volume of plastic in each plug (average 13.2 mm3), calculated from the length, cross-sectional area, and degree of the stenosis, showed a better correlation (r = .90, SEE = 2 mm3) with the actual plastic volume.(ABSTRACT TRUNCATED AT 250 WORDS)
The usefulness of x-ray computed tomography for the diagnosis of myocardial infarction.
Authors: Masuda Y , Yoshida H , Morooka N , Watanabe S , Inagaki Y
Published: June 2011

Conventional and enhanced computed tomographic (CT) examinations were performed in 103 patients with myocardial infarction for evaluation of the diagnostic usefulness of CT. After intravenous bolus injection of contrast material, an initial filling defect and late enhancement of the infarcted myocardium appeared on the cardiac CT images. These two findings were direct evidence of myocardial infarction; the former was found mostly in the patient with recent myocardial infarctions, and the latter was recognized both in those with recent and those with "remote" infarctions. Wall thinning at the site of infarction was found by enhanced CT mostly in patients with anteroseptal or extensive anterior infarctions, and was rarely found in patients with inferoposterior infarctions. Left ventricular aneurysms and ventricular thrombi were found by enhanced CT in 39 and 23 of the 103 subjects, respectively, and the sensitivity of CT in detecting intracardiac thrombi was higher than that of two-dimensional echocardiography. Calcification of the myocardium and pericardial effusion associated with myocardial infarction were also detected by conventional nonenhanced CT. Thus, cardiac CT was found to be a useful test in evaluating patients with myocardial infarction.
Identification of patients with ventricular tachycardia after myocardial infarction: signal-averaged electrocardiogram, Holter monitoring, and cardiac catheterization.
Authors: Kanovsky M S , Falcone R A , Dresden C A , Josephson M E , Simson M B
Published: June 2011

Electrocardiographic signal averaging techniques have demonstrated a low-amplitude late potential and a long filtered QRS complex in patients with ventricular tachycardia (VT) after myocardial infarction. Complex ventricular ectopy and left ventricular aneurysms have also been associated with VT. The purposes of this study were (1) to determine whether the findings from the signal-averaged electrocardiogram (ECG) were independent of those from Holter monitoring and cardiac catheterization and (2) to determine the combination of findings from the signal-averaged ECG, cardiac catheterization, and Holter monitoring that best characterize patients with VT after myocardial infarction. We studied 174 patients after myocardial infarction, 98 of whom had recurrent sustained VT. By multivariate logistic regression only three parameters were found to be independently significant, listed in order of power: positive signal-averaged ECG (presence of a late potential or a long filtered QRS duration), peak premature ventricular contraction greater than 100/hr, and presence of a left ventricular aneurysm (p less than .001). The signal-averaged ECG provides independent information in identifying patients with VT after myocardial infarction.
Calcium-channel blockade with nifedipine and angiotensin converting-enzyme inhibition with captopril in the therapy of patients with severe primary hypertension.
Authors: Guazzi M D , De Cesare N , Galli C , Salvioni A , Tramontana C , Tamborini G , Bartorelli A
Published: June 2011

Nifedipine (10 mg qid) and captopril (25 mg qid) were tested alone and in combination in 14 patients suffering from severe primary hypertension. Each study period was of 1 week's duration. Circulatory response was evaluated through hourly pressure and pulse rate readings. The fall in pressure after oral nifedipine was maximal within 1 hr or less and was generally accompanied by palpitation and increase in pulse rate; with a six hourly dosing regimen the tendency of blood pressure to recover after each dose was interrupted by the next dose, so that values remained significantly reduced throughout the 24 hr, although pressure fluctuations were evident. Promptness of the antihypertensive action of captopril was similar, but the magnitude and the duration of the fall in pressure were less pronounced. When the converting-enzyme inhibitor was combined with the calcium-channel blocker, pressure fluctuations were not abolished, but the antihypertensive response was definitely enhanced, so that normal blood pressure was maintained for several hours during the day. Additional positive effects of captopril were mitigation of the heart rate reaction and prevention of the ankle pitting or edema elicited by nifedipine. A balance in arteriolar and venular dilatation promoted by captopril is the suggested mechanism for these effects. With the two-drug combination the function of the left ventricle was not reduced and possibly improved; blood urea nitrogen and serum electrolyte and creatinine concentration were not affected. Plasma renin activity increased with captopril and reverted toward baseline with the addition of nifedipine, suggesting an interference of the calcium-channel blocker with the release of renin.
Sex-related differences in the normal cardiac response to upright exercise.
Authors: Higginbotham M B , Morris K G , Coleman R E , Cobb F R
Published: June 2011

In previous studies from this laboratory, we found that approximately 30% of women with chest pain and normal coronary arteries demonstrated either a decrease in or a failure to increase radionuclide ejection fraction during exercise. To examine the hypothesis that this apparent abnormality in left ventricular function represents a physiologic difference between men and women, we prospectively studied central and peripheral cardiovascular responses to exercise in 31 age-matched healthy volunteers (16 women and 15 men). A combination of quantitative radionuclide angiography and expired-gas analysis was used to measure ejection fraction and relative changes in end-diastolic counts, stroke counts, count output, and arteriovenous oxygen difference during symptom-limited upright bicycle exercise. Normal male and female volunteers demonstrated comparable baseline left ventricular function and similar aerobic capacity, as determined by weight-adjusted peak oxygen consumption (22.1 +/- 5.1 and 22.6 +/- 4.3 ml/kg/min, respectively). However, their cardiac responses to exercise were significantly different. Ejection fraction increased from 0.62 +/- 0.09 at rest to 0.77 +/- 0.07 during exercise in men (p less than .001), but was unchanged from 0.63 +/- 0.09 at rest to 0.64 +/- 0.10 during exercise in women. The ejection fraction increased by 5 points or more in 14 of 15 men, but in only seven of the 16 women. End-diastolic counts increased by 30% in women (p less than .001), but was unchanged in men. Because decreases in ejection fraction were matched by increases in end-diastolic counts, relative increases in stroke counts and count output were the same for men and women. These data demonstrate a basic difference between men and women with respect to the mechanism by which they achieve a normal response of stroke volume to exercise; these differences must be taken into account when measurements of cardiac function during exercise stress are used for diagnostic purposes.
Preexcited reciprocating tachycardia in patients with Wolff-Parkinson-White syndrome: incidence and mechanisms.
Authors: Bardy G H , Packer D L , German L D , Gallagher J J
Published: June 2011

During the electrophysiologic study of 435 patients referred for evaluation of Wolff-Parkinson-White syndrome, 42 (10%) had preexcited reciprocating tachycardia (defined as a macro-reentrant tachycardia that used an accessory atrioventricular [AV] pathway for antegrade conduction). The ages of the patients ranged from 9 to 67 years (27 +/- 14). Thirty-three were male patients, nine female, and eight had Ebstein's anomaly. Preexcited reciprocating tachycardia cycle length was 220 to 430 msec (294 +/- 42). Significant hemodynamic compromise in the laboratory directly related to preexcitated reciprocating tachycardia occurred in only one patient. However, in 10 patients a transformation to atrial fibrillation was seen after a spontaneously occurring premature atrial contraction. Only 17 of the 42 patients with preexcited reciprocating tachycardia during electrophysiologic study had the same tachycardia documented clinically. These 17 patients were more often younger with multiple accessory pathways and with no history of orthodromic reciprocating tachycardia when compared with 25 patients in whom preexcited reciprocating tachycardia could be induced only in the laboratory. Preexcited reciprocating tachycardia was induced in the laboratory in 22 of 374 (6%) patients with single accessory pathways and in 20 of 61 (33%) of those with multiple accessory pathways. In the 20 patients with multiple accessory pathways, the spectrum of reentrant circuits included fusion over two or more accessory pathways or fusion over both an accessory pathway and the AV node. In the 22 patients with a single accessory pathway and true antidromic reciprocating tachycardia, all but two episodes were at least 4 cm from the AV node. No patient with true antidromic reciprocating tachycardia had a posterior septal accessory AV pathway. Only in patients with multiple accessory pathways was the posterior septal accessory AV pathway used as the antegrade limb.
Retrograde concealed conduction in the atrioventricular node: differential manifestations related to level of intranodal penetration.
Authors: Lehmann M H , Mahmud R , Denker S , Soni J , Akhtar M
Published: June 2011

Although concealed conduction in the atrioventricular node (AVN) has been the focus of numerous experimental and clinical studies, little is known about the differential effects on AVN functional behavior of prior concealed retrograde impulse penetration alone vs prior anterograde or dual AVN activation. This study was undertaken specifically to investigate this aspect of human AVN physiology in patients without intact ventriculoatrial conduction to provide a model with which to analyze concealed retrograde AVN conduction. In 13 such patients AVN behavior during a subsequent anterograde input was characterized for each of three different manners of prior AVN activation: anterograde alone (method I), simultaneous anterograde and retrograde excitation (method II), or equivalently timed retrograde concealed AVN penetration alone (method III). In all patients evidence for retrograde AVN concealment was documented by longer anterograde conduction in the AVN during method III than that observed when the retrograde impulse was omitted (method IV). Furthermore, in these patients lacking intact ventriculoatrial conduction, anterograde conduction in the AVN was facilitated and refractoriness was decreased during dual excitation vs anterograde activation alone (method II vs method I). However, when each of methods I and II were compared with concealed retrograde AVN penetration alone (method III), two patterns of AVN responses were observed: In 11 of 13 patients (group A) conduction in the AVN was "worse" and refractoriness was greater both in methods I and II compared with method III; in the remaining two patients (group B) the opposite relationships were observed. The results suggest that among patients with no ventriculoatrial AVN conduction there exist at least two subpopulations whose AVN functional characteristics differ markedly when the effects of anterograde and dual excitation are compared with equivalently timed concealed retrograde activation alone. These findings may be related to differences in level of retrograde AVN concealment in groups A and B, which can be unmasked by the outlined pacing techniques.
Pulsed Doppler echocardiographic determination of stroke volume and cardiac output: clinical validation of two new methods using the apical window.
Authors: Lewis J F , Kuo L C , Nelson J G , Limacher M C , Quinones M A
Published: June 2011

Two methods of measuring stroke volume and cardiac output with pulsed Doppler two-dimensional echocardiography were developed and validated against the thermodilution technique in 39 patients, 33 of which were in an intensive care unit. With the use of the apical four-chamber view, a mitral inflow method combined the velocity of left ventricular inflow at the mitral anulus with the cross-sectional area of the anulus calculated from its diameter at middiastole (area = pi r2). From the apical five-chamber view a left ventricular outflow method combined the velocity of left ventricular outflow with the cross-sectional area of the aortic anulus calculated from its diameter during early systole (parasternal long-axis view). Measurements with the mitral inflow and left ventricular outflow methods were obtained in 35 of 39 (90%) and 39 of 39 (100%) patients, respectively. Validation of the mitral method excluded patients with mitral regurgitation (n = 11) and validation of the left ventricular outflow method excluded those with aortic regurgitation (n = 4). Good correlations were observed between thermodilution and Doppler measurements of stroke volume and cardiac output for both the mitral anulus method (R = .96 and .87, respectively) and the left ventricular outflow method (R = .95 and .91, respectively). The results of the two methods correlated well with each other in patients without regurgitant valve lesions. A greater interobserver variability was observed with the mitral anulus method, which was related solely to greater variability in measuring the annular diameter.(ABSTRACT TRUNCATED AT 250 WORDS)
Echocardiography in the diagnosis and management of symptomatic aortic valve stenosis in infants.
Authors: Huhta J C , Latson L A , Gutgesell H P , Cooley D A , Kearney D L
Published: June 2011

Infants with severe aortic valve stenosis often are critically ill and require urgent surgical treatment. Currently, angiography is used at the time of cardiac catheterization to diagnose aortic valve stenosis. However, the use of this test may be hazardous in an unstable infant and may precipitate hemodynamic and clinical deterioration before surgery. Therefore, a noninvasive method of accurately making this diagnosis would be useful in that it would allow the risks of cardiac catheterization to be avoided. Between January 1982 and September 1983, 10 infants with critically severe aortic valve stenosis and intact ventricular septum were examined by echocardiography. There were no false-positive or negative results in this time period and several criteria for the noninvasive diagnosis of critical aortic valve stenosis were recognized. These included immobile aortic valve cusps and left ventricular hypertrophy with increased echo density of the left ventricular papillary muscles and mitral valve support apparatus. Patients without other aortic obstruction had poststenotic dilation of the ascending aorta, as evidenced by a ratio of the diameter of the ascending aorta to that of aortic valve anulus greater than 1.7. A disturbed Doppler velocity signal in the ascending aorta supported the presence of valvar stenosis. Nine patients underwent cardiac surgery and five survived. In five patients surgery was performed without angiographic examination. The correct diagnosis was made noninvasively in each, and four of the five patients survived surgery. Echocardiography was comparable to angiography in making the diagnosis and assessing the cardiovascular anatomic characteristics. Echocardiography could therefore replace angiography in selected infants with symptomatic aortic valve stenosis and should be routinely used in the evaluation of these patients.
Stress echocardiography with transesophageal atrial pacing: preliminary report of a new method for detection of ischemic wall motion abnormalities.
Authors: Chapman P D , Doyle T P , Troup P J , Gross C M , Wann L S
Published: June 2011

We performed two-dimensional echocardiography in 19 patients with significant coronary artery disease and in six normal volunteers at rest and during transesophageal atrial pacing. Technically adequate resting echocardiograms were obtained in 18 of the 19 patients and in all six normal volunteers. In two subjects, atrial capture was not possible, and in one subject, discomfort from the pacing at the beginning of the study precluded its completion. In all subjects (n = 21) who completed the protocol satisfactory two-dimensional echocardiograms were obtained during pacing. Wall motion was normal at rest and during atrial pacing in five normal volunteers. New transient wall motion abnormalities developed in 13 of the 16 patients during pacing. Twelve of the 13 patients had significant coronary lesions in the coronary arteries supplying the abnormal wall segment. Only three of the patients developed significant ST segment depression during pacing. We conclude that stress echocardiography with transesophageal atrial pacing is safe and practical and can be used in patients who cannot perform dynamic exercise, this technique can detect ischemic segmental wall motion abnormalities corresponding to the distribution of coronary arterial obstruction, and the technique provides high-quality echocardiographic images during stress and thus may expand the usefulness of resting two-dimensional echocardiography in patients who have ischemic heart disease.