bluuebunny/crossref_metadata_2025 huggingface dataset:
Beneficial effects of dopamine combined with intravenous nitroglycerin on hemodynamics in patients with severe left ventricular failure.
Authors: Loeb H S , Ostrenga J P , Gaul W , Witt J , Freeman G , Scanlon P , Gunnar R M
Published: June 2011

Hemodynamic effects of dopamine and intravenous nitroglycerin alone, and in combination, were studied in 27 patients with severe left ventricular failure. Dopamine alone increased cardiac index from 1.8 to 2.5 l/min/m2 but also increased wedge pressure from 24 to 30 mm Hg and heart rate from 88 to 101 beats/min. Arterial oxygen saturation fell from 92% to 87% (p less than .001). Nitroglycerin alone had a lesser effect on cardiac index (1.8 to 2.2 l/min/m2) but decreased wedge pressure from 26 to 16 mm Hg and heart rate from 91 to 86 beats/min. Arterial oxygen saturation fell from 91% to 90% (NS). Combined dopamine and nitroglycerin administration resulted in optimal hemodynamics, with cardiac index of 2.9 l/min/m2, wedge pressure of 17 mm Hg, and heart rate of 96 beats/min. Arterial oxygen saturation remained low at 88% in spite of the reduction in left ventricular filling pressure, which probably reflects increased intrapulmonary right-to-left shunting coupled with increased pulmonary blood flow. These results suggest that the combination of dopamine with intravenous nitroglycerin should be considered for patients with severe left ventricular dysfunction who require temporary pharmacologic support.
Effects of nifedipine on coronary hemodynamic findings during exercise in patients with stable exertional angina.
Authors: Specchia G , de Servi S , Falcone C , Angoli L , Gavazzi A , Bramucci E , Mussini A , Ferrario M , Salerno J , Montemartini C
Published: June 2011

To investigate the mechanism by which nifedipine improves exercise tolerance in patients with coronary artery disease, we studied 14 patients with stable exertional angina and left anterior descending artery disease by measuring great cardiac vein flow (GCVF) and calculating anterior regional coronary resistance (ARCR) during exercise before and after sublingual administration of 20 mg of nifedipine. After nifedipine seven patients (group I) had no increase in exercise capacity and showed a similar magnitude of ST segment depression at peak exercise, while another seven patients (group II) had prolonged exercise duration (p less than .001) with less ST segment depression at peak exercise (p less than .01). Such effects were achieved despite a significant increase in double product, an indirect index of myocardial oxygen consumption. In group I patients no significant change was induced by nifedipine in GCVF or in ARCR either at rest or at peak exercise. In contrast, in group II patients nifedipine significantly increased GCVF at rest (p less than .05) and at peak exercise (p less than .001). Moreover, resting ARCR was decreased (p less than .01) and remained significantly lower at peak exercise (p less than .01) compared with the prenifedipine values. These data show that nifedipine may increase GCVF and decrease ARCR at rest and at peak exercise in patients with left anterior descending artery disease. Such increase in myocardial oxygen supply seems the most likely mechanism by which nifedipine may improve exercise capacity in patients with stable exertional angina.
Tolerance to isosorbide dinitrate: rate of development and reversal.
Authors: Parker J O , Fung H L , Ruggirello D , Stone J A
Published: June 2011

The circulatory response and plasma concentrations of isosorbide dinitrate (ISDN) were determined in 10 patients with chronic, stable angina after administration of 5 mg of sublingual ISDN during the control stage, after 48 hr of therapy with 15 mg of ISDN orally every 6 hr, and subsequently after a 48 hr period when ISDN was substituted by placebo four times daily. Initially, sublingual ISDN induced major reductions in both supine and standing systolic and diastolic blood pressure, but after 45 hr of therapy with oral ISDN, there was a significantly diminished vasodepressor response in both positions. Subsequently, when placebo was substituted for ISDN, the circulatory response initially seen was restored within 21 hr. Plasma ISDN concentrations after the test sublingual dose were slightly higher after 48 hr of oral ISDN dosing (i.e., the tolerant state) than at the start of the study. This suggests that tolerance is unlikely to be caused by reduced bioavailability or accelerated elimination of ISDN. It is possible that tolerance is related to accumulation of ISDN metabolites. The attenuation of the circulatory response to ISDN may be related to the altered antianginal efficacy commonly seen during sustained therapy with ISDN.
Balloon occlusion of atrial septal defect to assess right ventricular capability in hypoplastic right heart syndrome.
Authors: Bass J L , Fuhrman B P , Lock J E
Published: June 2011

Early surgery for forms of hypoplastic right heart syndrome may increase right ventricular size but could leave the patient with a residual right-to-left atrial shunt. Previous attempts to assess the capability of the right ventricle to accept systemic venous return have relied on angiographic estimates of tricuspid valve and right ventricular sizes. Since the minimum adequate sizes have not been established, we used a more physiologic technique of temporarily occluding the interatrial communication with a balloon-tipped catheter at cardiac catheterization in six consecutive patients. Five patients tolerated complete occlusion, although the tricuspid valve anulus diameter was less than the fifth percentile in all, and right ventricular volume was less than the fifth percentile in four. These five underwent surgical closure of an interatrial communication without evidence of postoperative systemic venous hypertension. Attempted occlusion in the sixth patient caused profound systemic venous hypoxia and surgical closure was not attempted. Temporary balloon occlusion may improve selection of patients for definitive operation.
Ultrasonic assessment of the St. Jude prosthetic valve: M mode, two-dimensional, and Doppler echocardiography.
Authors: Weinstein I R , Marbarger J P , Pérez J E
Published: June 2011

To determine whether the flow characteristics of aortic and mitral St. Jude Medical valves could be defined noninvasively, we analyzed Doppler transprosthetic flow velocity spectra in 23 relatively asymptomatic patients. Results were interpreted in the framework of M mode and two-dimensional echocardiographic data and were compared with Doppler transvalvular flow velocity spectra from native valves of healthy subjects. Although the morphologic characteristics of Doppler spectra were similar, peak and mean transprosthetic mitral flow velocities were higher than values obtained across native valves (1.38 +/- 0.3 m/sec and 0.73 +/- 0.1 m/sec vs 0.78 +/- 0.1 m/sec and 0.35 +/- 0.06 m/sec, respectively; p less than .001). However, calculated pressure half-times were not different (61.2 +/- 16.9 msec vs 57.2 +/- 13.2 msec; p greater than .05) and calculated transprosthetic mitral gradients were small (2.3 +/- 0.9 mm Hg). Similarly, the morphologic characteristics of aortic Doppler flow spectra in St. Jude and native valves were analogous. However, prosthetic valves exhibited higher peak and mean velocities (p less than .01) and slightly prolonged time-to-peak flow (p = .02). M mode and two-dimensional studies did not show useful quantitative measures of prosthetic function and did not demonstrate evidence of paravalvular leaks, which were detected in four cases by Doppler techniques. Thus Doppler echocardiography provides quantitative information about transprosthetic flow characteristics in patients with implanted St. Jude valves and is useful in identifying patients with prosthetic dysfunction.
Direct endocardial recording from an accessory atrioventricular pathway: localization of the site of block, effect of antiarrhythmic drugs, and attempt at nonsurgical ablation.
Authors: Jackman W M , Friday K J , Scherlag B J , Dehning M M , Schechter E , Reynolds D W , Olson E G , Berbari E J , Harrison L A , Lazzara R
Published: June 2011

We recorded a discrete 0.95 mV potential consistent with accessory atrioventricular pathway (AP) activation during serial electrophysiologic studies in a patient with Ebstein's anomaly and Wolff-Parkinson-White syndrome. Bipolar pacing from the catheter electrode in which the AP potential was recorded resulted in a stimulus-ventricle interval identical to the AP-ventricle interval during antegrade conduction, and a stimulus-atrium interval identical to the AP-atrium interval during retrograde conduction. With the patient in the drug-free state, antegrade AP block during atrial pacing and retrograde AP block during ventricular pacing occurred distal to the AP potential (AP-ventricle junction and AP-atrium junction, respectively), supporting the "impedance mismatch" hypothesis. Procainamide and disopyramide each lengthened the antegrade AP effective refractory period by affecting the AP-ventricle junction (possibly by decreasing the current generated by the AP). Both drugs also lengthened the retrograde AP effective refractory period but produced a greater effect on the ventricle-AP junction than on the AP-atrium junction, suggesting marginal geometry of the former. R wave synchronous shocks of 160 and 320 W-sec delivered between the catheter electrode recording the largest unipolar AP potential and a skin electrode produced transient, complete, antegrade block over the AP, suggesting the feasibility of this new nonsurgical technique for AP ablation.
Incomplete filling and incoordinate contraction as mechanisms of hypotension during ventricular tachycardia in man.
Authors: Lima J A , Weiss J L , Guzman P A , Weisfeldt M L , Reid P R , Traill T A
Published: June 2011

We sought to determine mechanisms for decrease of cardiac output and for hypotension during ventricular tachycardia (VT) in man. Two-dimensional and M mode echocardiograms and left ventricular pressure from micromanometer-tipped catheters were obtained in 20 patients before, during, and at the end of induced hypotensive VT. Patients were divided into two groups according to left ventricular function in sinus rhythm as assessed by angiographic ejection fraction (EF) before electrophysiologic study. Group 1 (n = 8) had angiographic EF greater than or equal to 50% in normal sinus rhythm, and group 2 (n = 12) had EF less than or equal to 40%. During VT, left ventricular cavity volume (as indexed by short- and long-axis two-dimensional end-diastolic cavity areas) was markedly reduced in group 1, from 19.7 +/- 2 to 8.6 +/- 2 cm2 (p less than .001) and from 32.0 +/- 8 to 22.5 +/- 7 cm2 (p less than .001), respectively, but was only slightly reduced in group 2, from 34.1 +/- 6 to 31.5 +/- 7 cm2 (p = .044) and from 45.0 +/- 8 to 49.4 +/- 7 cm2 (p = NS), respectively. Conversely, left ventricular systolic function during VT (as indexed by fractional reduction in two-dimensional short- and long-axis areas) was markedly depressed in group 2, from 25.6 +/- 6% to 4.2 +/- 4% (p = .005) and from 13.7 +/- 3% to 1.8 +/- 0.8% (p less than .001), respectively, but remained at control levels in group 1. Left ventricular end-diastolic pressures increased in group 1, from 11.8 +/- 2 to 27.7 +/- 8 mm Hg (p = .005) and did not change in group 2 during VT. Pressure-dimension loops from left ventricular pressure and M mode echocardiographically determined cavity dimensions generated from the end of the VT episodes showed that diastolic pressure-dimension relationships returned to control levels with the first prolonged diastolic interval in group 1 patients, indicating that incomplete relaxation was the mechanism responsible for reduction of cardiac output during VT in these patients. Coordination of contraction and relaxation (indicated by the percent ratio of the pressure-dimension loop area to the area of the rectangle just enclosing the loop) decreased from 37 +/- 11% to 16 +/- 13% in group 2 patients during VT (p = .013) but remained at control levels in group 1 patients. Thus, during VT patients with impaired left ventricular function in sinus rhythm (group 2) developed severe discoordination, and patients with normal or near-normal function (group 1) developed incomplete relaxation to account for stroke volume deterioration and hypotension.
The prognosis for patients with new-onset angina who have undergone cardiac catheterization.
Authors: Roberts K B , Califf R M , Harrell F E , Lee K L , Pryor D B , Rosati R A
Published: June 2011

We investigated the prognostic significance of new-onset angina in patients in whom coronary anatomic characteristics were known. New onset angina was defined as angina of less than 3 months duration. Consecutive patients (n = 1727) with significant coronary artery disease (diagnosed at cardiac catheterization) and who had not had a prior myocardial infarction or congestive heart failure were studied. In patients with new-onset angina (n = 329) there was a higher incidence of single-vessel disease (43% vs 27%) and a lower incidence of triple-vessel (23% vs 35%) and left main artery (5% vs 10%) disease compared with patients with chronic angina (n = 1398). Patients were classified by the presence or absence of preinfarction angina (severe and prolonged angina at rest requiring hospitalization to rule out myocardial infarction). In patients treated without surgery and who did not have preinfarction angina, survival at 1 year was 97% for patients with new-onset angina and 98% for those with chronic angina (p = .27). Among patients not treated surgically who did not have preinfarction angina, at 1 year 16% with new-onset angina and 7% with chronic angina had suffered a cardiac event (nonfatal myocardial infarction or death, p = .006). In patients treated surgically who did not have preinfarction angina, survival at 1 year was 96% both for those with new-onset angina and those with chronic angina (p = .99). The risk of an event in patients treated surgically at 1 year was not statistically different in patients with new-onset angina and those with chronic angina (12% vs 11%, p = .27). Survival and event-free rates were lower in patients with preinfarction angina than in patients who did not have it.(ABSTRACT TRUNCATED AT 250 WORDS)
Exercise testing provides additional prognostic information in angiographically defined subgroups of patients with coronary artery disease.
Authors: Gohlke H , Samek L , Betz P , Roskamm H
Published: June 2011

We examined whether exercise testing with measurement of cardiac output during maximal exercise can provide additional prognostic information for medically treated patients in whom left ventricular function and extent of coronary artery disease are known. We followed 1034 patients with normal or mildly impaired left ventricular function; 410 of these patients (group 1) had single-vessel disease, 316 had double-vessel disease (group 2), and 308 had triple-vessel disease (group 3). In addition, 204 patients with double- or triple-vessel disease and moderately impaired left ventricular function (group 4) were followed. Mean follow-up in these 1238 patients was 4.5 years. End point of follow-up was death. Groups 1, 2, and 3 were divided into terciles according to the maximally achieved values of the following exercise variables: exercise tolerance, angina-free exercise tolerance, maximal heart rate, and cardiac output during maximal exercise. Group 4 was divided into halves accordingly. Survival curves (according to the method of Cutler and Ederer) for group 2 showed a 15% difference in 5 year survival rate between the highest and lowest terciles (p less than .005) by use of the noninvasive variables exercise tolerance, angina-free exercise tolerance, and maximal heart rate (95% vs 80%). The separation into terciles according to cardiac output during maximal exercise resulted in a significant difference in survival rates between the highest and lowest terciles (halves) in all groups of patients. The differences in 5 year survival rates were 9% (p less than .05), 16% (p less than .05), and 19% (p less than .005) for groups 1, 2, and 3, respectively, and 22% for group 4 (p less than .005).(ABSTRACT TRUNCATED AT 250 WORDS)
Results of endomyocardial biopsy in patients with spontaneous ventricular tachycardia but without apparent structural heart disease.
Authors: Strain J E , Grose R M , Factor S M , Fisher J D
Published: June 2011

To evaluate possible occult myocardial disease in 18 patients whose only major manifestation of heart disease was spontaneous ventricular tachycardia or fibrillation, right ventricular endomyocardial biopsies were performed. None of the patients had symptoms of ischemic or congestive heart disease, and at catheterization none had significant lesions of the coronary arteries or regional wall motion abnormalities of the left ventricle. The mean left ventricular ejection fraction (65 +/- 7%), mean right ventricular ejection fraction (55 +/- 9%), mean cardiac index (3.0 +/- 0.5 1/min/m2), mean right atrial pressure, mean pulmonary capillary wedge pressure, and mean pulmonary artery systolic pressure were normal. However, right ventricular endomyocardial biopsy specimens were abnormal in 16 of 18 (89%) patients: nine (50%) had changes of a significant, although nonspecific, cardiomyopathy with myocellular hypertrophy, interstitial and perivascular fibrosis, and vascular sclerosis; three (17%) had subacute inflammatory myocarditis; two (11%) had diffuse abnormalities of the intramyocardial arteries; and two (11%) had pathologic changes consistent with arrhythmogenic right ventricular dysplasia. In the two (11%) patients with normal biopsy specimens, one had Wolff-Parkinson-White syndrome and the other had mitral valve prolapse. Although histologic abnormalities were found in 89% of these patients, performance of right ventricular endomyocardial biopsies in this group of patients should be considered a research procedure. We conclude that the majority of patients who have serious ventricular arrhythmias but no apparent structural cardiac abnormalities have abnormal right ventricular biopsy specimens and that the arrhythmias may be the first manifestation of a variety of primary myocardial abnormalities.
Persistent reduction in left ventricular asynergy in patients with acute myocardial infarction by intravenous infusion of nitroglycerin.
Authors: Jugdutt B I , Sussex B A , Warnica J W , Rossall R E
Published: June 2011

Intravenous nitroglycerin (NG) infusion in patients with acute myocardial infarction (AMI) has been shown to improve left ventricular function and myocardial perfusion and to decrease ischemic injury and creatine kinase (CK) indexes of infarct size. To determine whether early NG infusions in patients with AMI decreases the extent of left ventricular asynergy, we used two-dimensional echocardiography to measure asynergic segments (akinesis and/or dyskinesis) at four serial short-axis levels from base to apex (mitral, M; chordal, C; midpapillary, MP; low papillary, LP) in 22 patients with a first anterior AMI. Patients were randomized between infusions of NG (n = 11) or 5% dextrose in water (controls, n = 11) within 5.6 hr after the onset of pain. NG infusion rates were titrated to lower mean arterial pressure to an average level of 7% below control (but not below 80 mm Hg) and were maintained at this level for the duration of the infusions (39 hr). After NG, left ventricular function improved as left ventricular filling pressure decreased (p less than .005), and sigma ST on precordial ST segment mapping decreased (p less than .001). These parameters did not change in control subjects. Computed CK infarct size was smaller in the NG group than in the control group (p less than .05). Before the infusions, the mean extent of left ventricular asynergy (% left ventricular circumference) were similar in both groups: M, 18% vs 21%; C, 22% vs 23%; MP, 26% vs 24%; LP, 32% vs 29%. In addition, the computed total left ventricular asynergy (% surface area) was also similar for these two groups before therapy (25% vs 25%). There was no change in left ventricular asynergy from pretreatment values by 1 hr and 10 days among control subjects: M, 18% vs 18% vs 17%; C, 22% vs 22%; MP, 26% vs 26% vs 22%; LP, 32% vs 33% vs 33%; total 25% vs 25% vs 24% (multiple measures analysis of variance). In contrast, there was a significant decrease (p less than .001) in left ventricular asynergy from pretreatment values by 1 hr and 10 days with NG: M, 21% vs 10% vs 8%; C, 23% vs 12% vs 10%; MP, 24% vs 13% vs 9%; LP, 29% vs 14% vs 10%; total, 25% vs 12% vs 9%.(ABSTRACT TRUNCATED AT 400 WORDS)
Reflected reentry in nonhomogeneous ventricular muscle as a mechanism of cardiac arrhythmias.
Authors: Rozanski G J , Jalifé J , Moe G K
Published: June 2011

Arrhythmogenesis in ventricular muscle exhibiting nonhomogeneous excitability was studied in isolated tissues from feline and canine hearts. Longitudinal bundles were mounted in a three-chambered bath and simultaneous transmembrane recordings were obtained from fibers in each chamber. Nonhomogeneous excitability was established by depressing only the central segment (1 to 2 mm wide) with high-K+ Tyrode's solution, which induced discontinuity of propagation associated with step delays mediated by electrotonic current flowing through the depressed zone. When transmission delays were long, activity distal to the site of block returned to proximal tissue as one of two forms of reflected reentry, each elicited by a different mechanism. Type I reflection, occurring with antegrade delays of 30 to 60 msec, was characterized by an early secondary depolarization due to electrotonic spread of currents from delayed responses in the depressed segment. Type II reflection evolved with delays greater than 90 msec and was manifest as a closely coupled regenerative action potential that developed independently of a pacemaker mechanism and of slow but continuous conduction. We conclude that delayed activation of excitable elements, which occurs when propagation is discontinuous, may lead to rhythm disturbances of focal origin that are mediated by electrotonic interactions across a zone of depressed tissue.
Relationship between central hemodynamics and regional blood flow in normal subjects and in patients with congestive heart failure.
Authors: Leithe M E , Margorien R D , Hermiller J B , Unverferth D V , Leier C V
Published: June 2011

Central and regional (hepatic, renal, and limb) hemodynamic data are presented for a normal population (n = 16) and for a group of patients with congestive heart failure (n = 64). The patient population represented a wide spectrum of severity of congestive heart failure. Various relationships between central and regional hemodynamics were analyzed. The results indicate that in congestive heart failure blood flow to hepatic, renal, and limb regions is significantly decreased, and that this decrease is proportional and linearly related to the reduction in cardiac output. The vascular resistances of these regions correlated directly with systemic vascular resistance. Changes in renal vascular resistance and renal blood flow became attenuated as the severity of the heart failure advanced from moderate to severe and at higher levels of systemic vascular resistance. There was little to no correlation between systemic blood pressure and liver, kidney, and limb blood flow for the range of systemic pressures studied.
alpha-Adrenergic receptors and coronary spasm: an elusive link.
Authors: Chierchia S , Davies G , Berkenboom G , Crea F , Crean P , Maseri A
Published: June 2011

In 14 consecutive patients with variant angina we investigated the possible role of coronary alpha-adrenergic receptors in the genesis of coronary spasm. In eight patients, computerized, beat-by-beat analysis of the electrocardiogram recorded during continuous Holter monitoring failed to reveal any increase of heart rate and corrected QT interval (both indexes of cardiac sympathetic activation) in the period preceding the onset of ST segment changes in 197 episodes of ischemia caused by coronary spasm. In the same patients, analysis of the circadian distribution of ischemic episodes revealed a significantly higher incidence in the early morning hours, when sympathetic activity is at the lowest level. Twelve patients underwent serial provocative testing with cold pressor, phenylephrine, or norepinephrine infusion and administration of ergonovine maleate. Ergonovine consistently reproduced coronary spasm in all 12 patients, while results of cold pressor testing were positive in only one. Infusion of phenylephrine (eight patients) or norepinephrine after beta-blockade (four patients) failed to precipitate myocardial ischemia. In five patients infusion of phentolamine at the highest tolerated dose did not reduce significantly the number of ischemic attacks when compared with placebo. In contrast to results of previous reports, our data seem to rule out the hypothesis that an increase of sympathetic outflow to the heart plays an important role in the genesis of coronary spasm. We cannot, however, exclude the possibility of localized alpha-stimulation of epicardial arteries.
The results of transvenous endomyocardial biopsy can frequently be used to diagnose myocardial diseases in patients with idiopathic heart failure. Endomyocardial biopsies in 100 consecutive patients revealed a substantial incidence of myocarditis.
Authors: Parrillo J E , Aretz H T , Palacios I , Fallon J T , Block P C
Published: June 2011

Transvenous endomyocardial biopsy is an accepted method to evaluate cardiac transplant rejection, but the clinical diagnostic value of the technique for other forms of cardiac disease has not been established. We performed biopsies in 100 consecutive patients without significant complications. The pathologic diagnostic information obtained was judged to be useful to the clinician in 54 and not useful in 46 patients. In 74 patients with congestive heart failure of unknown etiology and a dilated heart, useful pathologic diagnoses included myocarditis, vasculitis, doxorubicin cardiomyopathy, and congestive cardiomyopathy. In most of the patients with biopsy findings of myocarditis there were no other clinical or laboratory findings indicating the presence of this disease, and the diagnosis of myocarditis would have been overlooked without a biopsy. In 26 patients in whom there was clinical evidence of constrictive or restrictive cardiovascular physiologic characteristics, useful biopsy diagnoses included radiation-induced cardiomyopathy, endomyocardial fibrosis, amyloidosis, or no myocardial disease; in the patients without myocardial disease thoracotomies were performed for constrictive pericarditis. Transvenous endomyocardial biopsy can provide clinically useful information in the evaluation of diseases of the myocardium.
Exercise cardiac output is maintained with advancing age in healthy human subjects: cardiac dilatation and increased stroke volume compensate for a diminished heart rate.
Authors: Rodeheffer R J , Gerstenblith G , Becker L C , Fleg J L , Weisfeldt M L , Lakatta E G
Published: June 2011

To assess the effect of age on cardiac volumes and function in the absence of overt or occult coronary disease, we performed serial gated blood pool scans at rest and during progressive upright bicycle exercise to exhaustion in 61 participants in the Baltimore Longitudinal Study of Aging. The subjects ranged in age from 25 to 79 years and were free of cardiac disease according to their histories and results of physical, resting and stress electrocardiographic, and stress thallium scintigraphic examinations. Absolute left ventricular volumes were obtained at each workload. There were no age-related changes in cardiac output, end-diastolic or end-systolic volumes, or ejection fraction at rest. During vigorous exercise (125 W), cardiac output was not related to age (cardiac output [1/min] = 16.02 + 0.03 [age]; r = .12, p = .46). However, there was an age-related increase in end-diastolic volume (end-diastolic volume [ml] = 86.30 + 1.48 [age]; r = .47, p = .003) and stroke volume (stroke volume [ml] = 85.52 + 0.80 [age]; r = .37, p = .02), and an age-related decrease in heart rate (heart rate [beats/min] = 184.66 - 0.70 [age]; r = -.50, p = .002). The dependence of the age-related increase in stroke volume on diastolic filling was emphasized by the fact that at this high workload end-systolic volume was higher (end-systolic volume [ml] = 3.09 + 0.65 [age]; r = .45, p = .003) and ejection fraction lower (ejection fraction = 88.48 - 0.18 [age]; r = -.33, p = .04) with increasing age. These findings indicate that although aging does not limit cardiac output per se in healthy community-dwelling subjects, the hemodynamic profile accompanying exercise is altered by age and can be explained by an age-related diminution in the cardiovascular response to beta-adrenergic stimulation.
Level, trend, and variability of blood pressure during childhood: the Muscatine study.
Authors: Lauer R M , Clarke W R , Beaglehole R
Published: June 2011

On alternate years from 1970 to 1981 blood pressure has been measured in school children living in Muscatine, Iowa. A total of 4313 children beginning at 5 to 14 years of age have been examined on three to six occasions. To compare blood pressures throughout the period of observation, each value was expressed as a percentile rank. For each subject the average percentile rank (level), the trend in rank, and the variability over time were calculated. Values for height, weight, relative weight, and triceps skinfold thickness were expressed in the same fashion. The relationship between average rank of blood pressure and average rank of body size as well as between trend of blood pressure and trend of body size percentiles were significant (p less than .05). These observations indicate the importance of relative rate of growth in the establishment of the rank order of blood pressure. Using the variables of level, trend, and variability, we identified groups of children who appear to be consistently tracking toward future hypertension: 233 (5.4%) children, whose systolic levels were in the upper quintile with either a flat or rising trend and low variability, and 280 (6.0%) children with systolic levels in the lower four quintiles with high trend and low variability. In addition there were 321 (7.4%) children whose mean systolic levels were in the upper quintile with high variability and who thus resemble adults with labile hypertension. There were similar numbers of children with diastolic pressures showing these features.
Effects of therapy with cholestyramine on progression of coronary arteriosclerosis: results of the NHLBI Type II Coronary Intervention Study.
Authors: Brensike J F , Levy R I , Kelsey S F , Passamani E R , Richardson J M , Loh I K , Stone N J , Aldrich R F , Battaglini J W , Moriarty D J
Published: June 2011

In the National Heart, Lung and Blood Institute Type II Coronary Intervention Study, patients with Type II hyperlipoproteinemia and coronary artery disease (CAD) were placed on a low-fat, low-cholesterol diet and then were randomly allocated to receive either 6 g cholestyramine four times daily or placebo. This double-blind study evaluated the effects of cholestyramine on the progression of CAD as assessed by angiography. Diet alone reduced the low-density lipoprotein cholesterol 6% in both groups. After randomization, low-density lipoprotein cholesterol decreased another 5% in the placebo group and 26% in the cholestyramine-treated group. Coronary angiography was performed in 116 patients before and after 5 years of treatment. CAD progressed in 49% (28 of 57) of the placebo-treated patients vs 32% (19 of 59) of the cholestyramine-treated patients (p less than .05). When only definite progression was considered, 35% (20 of 57) of the placebo-treated patients vs 25% (15 of 59) of the cholestyramine-treated patients exhibited definite progression; the difference was not statistically significant. However, when this analysis was performed with adjustment for baseline inequalities of risk factors, effect of treatment was more pronounced. Of lesions causing 50% or greater stenosis at baseline, 33% of placebo-treated and 12% of cholestyramine-treated patients manifested lesion progression (p less than .05). Similar analyses with other end points (percent of baseline lesions that progressed, lesions that progressed to occlusion, lesions that regressed, size of lesion change, and all cardiovascular end points) all favored the cholestyramine-treated group, but were not statistically significant. Thus, although the sample size does not allow a definitive conclusion to be drawn, this study suggests that cholestyramine treatment retards the rate of progression of CAD in patients with Type II hyperlipoproteinemia.
Electrophysiologic substrate for ventricular tachycardia: correlation of properties in vivo and in vitro.
Authors: Richards D A , Blake G J , Spear J F , Moore E N
Published: June 2011

Cardiac electrophysiologic studies were performed in three control dogs and in nine dogs with previous (8 to 22 days) anterior myocardial infarction. During programmed stimulation, no control dog had more inducible ventricular fibrillation (VF) or tachycardia (VT), three dogs with infarcts had inducible VF and six had inducible VT. Recordings in vivo were made via a plaque electrode containing 10 bipolar electrodes (3.0 x 1.5 cm) placed on the epicardial surface of the anteroapical left ventricle. Subsequently, epicardial strips (2 mm thick) from beneath the plaque were prepared for studies in vitro. Electrogram durations were significantly greater in dogs with infarcts than in control dogs both in vivo (p less than .05) and in vitro (p less than .001). Electrogram amplitudes were significantly lower in dogs with VT in vivo (p less than .05) and in vitro (p less than .001). In control animals activation was continuous and most rapid in the direction of fiber orientation; there were areas of slow and/or discontinuous conduction in all dogs with infarcts. In one case, sustained reentrant beating in vitro was caused by functional unidirectional block and microreentry at a site of continuous electrical activity during VT in vivo. Reentrant beating in vitro persisted in 0.5 cc of isolated tissue. We conclude that broad low-amplitude electrograms in vivo and in vitro depict local areas of slow and/or discontinuous conduction, that the intrinsic asymmetry of cardiac activation due to fiber orientation is accentuated by infarction and may predispose to intraventricular reentry, and that intraventricular reentrant circuits that may be present on the epicardial surface may persist in a volume of myocardial tissue as small as 0.5 cc.
Sodium susceptibility and potassium effects in young patients with borderline hypertension.
Authors: Fujita T , Noda H , Ando K
Published: June 2011

To evaluate sodium susceptibility in subjects with borderline hypertension at increased risk of developing essential hypertension, the effect of salt loading after sodium deprivation with a diuretic was studied in 21 young patients with borderline hypertension and 12 age-matched normal subjects. Treatment with a diuretic caused significant decreases in mean blood pressure (MBP) in subjects with borderline hypertension but not in normotensive subjects. In borderline hypertensives, the subsequent sodium loads resulted in a significant rise in MBP (5.8 +/- 1.7%; p less than .01), but sodium did not change MBP in normotensives. There is a good correlation between the increments in MBP with sodium loads and the decrements in MBP with a diuretic for each patient (r = -.759, p less than .001). After diuretics, cardiac index (CI) as measured echocardiographically fell significantly but calculated total peripheral resistance (TPR) remained unchanged in subjects with borderline hypertension. After 180 meq sodium chloride each day was added for 7 days, CI (9.1 +/- 2.1%; p less than .01) and stroke index (21.0 +/- 3.4%; p less than .01) rose significantly but TPR remained unchanged. Overall, the increments of MBP with sodium loads did not correlate with the changes in CI but did correlate with the changes in TPR (r = .567, p less than .01). In these young patients with borderline hypertension, plasma norepinephrine and epinephrine concentrations and plasma renin activity (PRA) were significantly higher than in normotensive subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
Percutaneous transluminal balloon valvuloplasty for pulmonary valve stenosis.
Authors: Kan J S , White R I , Mitchell S E , Anderson J H , Gardner T J
Published: June 2011

Transluminal balloon valvuloplasty was used to treat congenital pulmonary valve stenosis in 20 patients. Follow-up cardiac catheterization was performed in 11 patients at intervals of from 2 to 12 months after the procedure. Peak systolic pressure gradient across the pulmonic valve decreased from 68 +/- 27 to 23 +/- 5 mm Hg (p less than .001) after valvuloplasty. There were no complications. Follow-up catheterization demonstrated persistent relief of right ventricular hypertension in the patients with typical pulmonary valve stenosis.
Long-term patency of the ductus arteriosus after balloon dilatation: an experimental study.
Authors: Lund G , Rysavy J , Cragg A , Salomonowitz E , Vlodaver Z , Zuniga W C , Amplatz K
Published: June 2011

Balloon dilatation of the ductus arteriosus was carried out in vivo in eight piglets that were 12 to 16 days old. The ductus was functionally closed in all animals before dilatation. Long-term patency for periods of up to 6 months after the procedure was demonstrated in six animals by angiography, Doppler ultrasound examination, and at autopsy. The presence of hemodynamically significant shunts was indicated by clinical development of heart failure, pulmonary infections, and left ventricular hypertrophy. These results confirm the value of this laboratory preparation to create left-to-right shunts at the ductus level.
Role of ischemia in contrast-induced renal damage: an experimental study.
Authors: Lund G , Einzig S , Rysavy J , Borgwardt B , Salomonowitz E , Cragg A , Amplatz K
Published: June 2011

Total and regional cortical blood flow was measured in dogs by the radioactive microsphere technique after renal damage of varying severity had been induced by combining selective injection of diatrizoate, iopamidol, or normal saline with a 10 min occlusion of the renal artery. There was extensive tubular and glomerular damage in the kidneys exposed to diatrizoate, but not in the kidneys exposed to saline. Iopamidol caused intermediate changes. Average cortical blood flow was reduced from baseline levels in all groups 5 min after perfusion was restored. After 1 hr the flow had returned to the baseline level. Analysis of variance did not show a statistically significant difference among the groups. A tendency for redistribution of flow from outer to inner cortical layers was seen, but this was present in all groups. The flow changes detected in this study cannot explain the varying severity of renal damage.
Volume-dependent effects of positive airway pressure on intracavitary left ventricular end-diastolic pressure.
Authors: Ditchey R V
Published: June 2011

To test the hypothesis that the effects of positive end-expiratory airway pressure (PEEP) on intracavitary left ventricular end-diastolic pressure (LVEDP) depend on the ventricular filling conditions under which PEEP is applied, the effects of PEEP on pressure in and around the left ventricle were determined before and after stepwise expansion of intravascular blood volume in 10 closed-chest dogs. Over a range of 0 to 20 cm of water, PEEP progressively increased both intrapericardial and intracavitary right ventricular end-diastolic pressures. These increases in pressure around the left ventricle were approximately linear and were relatively unaffected by volume loading. At the same time, PEEP always decreased transmural LVEDP by decreasing ventricular filling. However, transmural LVEDP fell more when ventricular volume was initially large, due to the nonlinear relationship between left ventricular transmural pressure and volume. As a result, intracavitary LVEDP (which reflected the sum of decreased transmural LVEDP and increased external pressure) increased when baseline ventricular volume was small and decreased when baseline ventricular volume was large. At intermediate volumes the fall in transmural pressure equaled the rise in external pressure, and intracavitary LVEDP did not change. These findings demonstrate that changes due to PEEP in intracavitary LVEDP are a complex function of increased intrathoracic pressure, decreased ventricular filling, and the operative level of left ventricular compliance.
Myocardial injury and induction of arrhythmia by direct current shock delivered via endocardial catheters in dogs.
Authors: Lerman B B , Weiss J L , Bulkley B H , Becker L C , Weisfeldt M L
Published: June 2011

Although electrical ablation of ventricular tachycardia via percutaneous catheters has been recently accomplished in human beings, little is known of its pathologic or arrhythmogenic effects. We studied 21 open-chest anesthetized dogs in which an endocardial electrode catheter was percutaneously introduced into the left ventricle. Direct current (DC) shock was delivered by a standard defibrillator through the distal electrode to a back paddle. Cross-sectional two-dimensional echocardiographic studies were performed in the plane of the catheter (confirmed by epicardial metal beads), and blood flow was determined by the microsphere technique before DC shock and when the animals were killed 2 to 8 days later. Of 11 dogs receiving a total of 100 to 400 J, only three survived 48 hr compared with nine of 10 receiving 50 J and all three control dogs. Holter monitoring demonstrated sustained ventricular tachycardia (VT) (greater than or equal to 30 sec) in all 11 dogs monitored (six received greater than or equal to 100 J), beginning within 5 hr of the DC shock; three control dogs had no VT. Two dogs that died suddenly while being monitored showed ventricular fibrillation. Histologic examination revealed hemorrhagic contraction band necrosis in the shock zone, a type of injury similar to that observed in reperfusion necrosis. Necrosis of the left ventricle was 0.5% to 5%. There was no significant difference in necrosis between dogs receiving 100 J or more and those receiving 50 J (2.5 vs 1.7 g; p greater than .10). Percent systolic thickening determined in eight equally divided regions around the left ventricle showed no difference between the shock zone, perishock zone, or remote normal zone in dogs receiving 50 J.(ABSTRACT TRUNCATED AT 250 WORDS)
The effects of milrinone on conduction, reflection, and automaticity in canine Purkinje fibers.
Authors: Davidenko J M , Antzelevitch C
Published: June 2011

Milrinone is a newly developed analogue of amrinone possessing potent positive inotropic action. Electrophysiologic actions of the drug have not been reported. In this study microelectrode techniques were used to assess the electrophysiologic effects of milrinone in canine false tendons homogeneously superfused with either normal or high-K Tyrode's solution and in Purkinje fibers mounted in a three-compartment chamber in which the central segment was depressed with an "ischemic" solution. Milrinone (0.2 to 20 micrograms/ml) caused no major changes in the action potential characteristics, refractoriness, or conduction velocity in fibers exposed to normal Tyrode's solution, but markedly improved conduction and abbreviated or eliminated postrepolarization refractoriness in the ischemic gap preparations. The drug also exerted important effects on reflected reentry generated in these preparations. Depending on the initial level of block, milrinone (1) suppressed the arrhythmia, (2) shifted its frequency dependence, or (3) created the conditions that allowed reflection to occur. Similar results were obtained in homogeneously depressed fibers. At similar concentrations, milrinone caused a relatively small enhancement of automaticity. Thus, in addition to its inotropic actions, milrinone produces important electrophysiologic effects. By restoring or improving conduction through areas of depressed conductivity, the drug may exert either antiarrhythmic or arrhythmogenic effects.
Two-dimensional echocardiographic examination of mitral valve abnormalities associated with coarctation of the aorta.
Authors: Celano V , Pieroni D R , Morera J A , Roland J M , Gingell R L
Published: June 2011

Coarctation of the aorta is frequently associated with left ventricular inflow tract abnormalities that may be difficult to detect even at cardiac catheterization. This study involved patients with coarctation who underwent comprehensive two-dimensional echocardiographic investigations emphasizing visualization of the mitral valve and its apparatus. Of the 56 patients studied, 23 had completely normal study results, while in 33 (59%) results showed abnormalities of the mitral complex. The latter were divided into two groups: those having major mitral abnormalities (n = 12) and those with minor anomalies of the valve and apparatus (n = 21). The first group included patients with a supravalve stenosing ring, congenital mitral stenosis, mitral valve prolapse, and parachute mitral valve. Minor anomalies were classified as abnormalities of the papillary muscles, chordae tendineae, or combinations of both. No mitral malformations were found in a control group of patients. We conclude that two-dimensional echocardiography is a sensitive and accurate noninvasive method for assessing either significant or subtle forms of left ventricular inflow disease in patients with aortic coarctation. Its use is recommended for the acute medical and surgical management of these patients as well as for their long-term follow-up evaluation.
Asynchronous left ventricular diastolic filling in patients with isolated disease of the left anterior descending coronary artery: assessment with radionuclide ventriculography.
Authors: Yamagishi T , Ozaki M , Kumada T , Ikezono T , Shimizu T , Furutani Y , Yamaoka H , Ogawa H , Matsuzaki M , Matsuda Y
Published: June 2011

To study the relationship between global and regional filling of the left ventricle, we conducted resting gated radionuclide ventriculographic studies in 15 control subjects (group 1) and 22 patients with isolated disease of the left anterior descending coronary artery (group 2). None had had a previous myocardial infarction. A computer program subdivided the image of the left ventricle into four regions. The time-activity and first-derivative curves of the global and regional left ventricles were computed. In the global left ventricle, the normalized peak filling rate (PFR) was decreased (p less than .01) and the ratio of the time to PFR (time interval from global end-systole to PFR) to the diastolic time, TPFR/DT, was greater (p less than .02) in group 2 than in group 1. In the regional left ventricle, in the side perfused by the stenosed vessel (septal and apical), PFR was slightly decreased in the apical (p less than .05), but not the septal region (p = NS); TPFR/DT was greater in the apical (p less than .02) and in the septal region (p less than .01) in group 2. In the normally perfused lateral side, there were no significant differences in PFR or in TPFR/DT between group 1 and group 2. Total delta t/DT, which was defined as the ratio of the sum of the absolute values of the time differences from global PFR to regional PFR (septal, apical, and lateral) to the diastolic time, was significantly greater in group 2 (0.09 +/- 0.05 vs 0.16 +/- 0.05; p less than .001). This indicates the existence of asynchronous diastolic filling in the different regions of the left ventricle in group 2. A negative correlation existed between total delta t/DT and global PFR (r = -.64, p less than .001). Thus, in patients with one-vessel disease, asynchronous diastolic filling occurs due to the filling disturbance in the affected regions, which may cause impairment of the filling of the global left ventricle.