bluuebunny/crossref_metadata_2025 huggingface dataset:
Coronary surgery after recurrent myocardial infarction: progress of a trial comparing surgical with nonsurgical management for asymptomatic patients with advanced coronary disease.
Authors: Norris R M , Agnew T M , Brandt P W , Graham K J , Hill D G , Kerr A R , Lowe J B , Roche A H , Whitlock R M , Barratt-Boyes B G
Published: June 2011

A randomized trial of surgical vs nonsurgical management was carried out in men 60 years of age or younger who had recovered from a recurrent myocardial infarction. Of 205 patients considered, 100 had few or no symptoms and had coronary vessels favorable for bypass grafting; these patients fulfilled the trial conditions and were randomized (50 surgical and 50 nonsurgical). In 41 patients (elective nonsurgical group), randomization was not considered justifiable because of relatively unfavorable coronary anatomy or severe left ventricular dysfunction. Nineteen patients had elective surgery because of disabling angina despite full medical treatment or because of significant left main coronary stenosis. In 45 patients, coronary angiography was not undertaken because of medical contraindications or reluctance of the patient to enter the study. Actuarial survival curves (mean follow-up 4.5 years) show an annual mortality rate of 3-4% per year for all investigated patients, and no advantage for the randomized surgical over the randomized nonsurgical group. The results suggest that in the absence of disabling angina or left main coronary artery stenosis, coronary artery surgery need not be advised for survivors of recurrent infarctions who have severe coronary artery disease. Moreover, the prognosis for the group of patients not treated surgically appears to be better than has been previously described.
Choice of electrocardiographic leads for recording the earliest QRS onset in noninvasive measurements.
Authors: Wanderman K L , Loutaty G , Ovsyshcher I , Cantor A , Gussarsky Y , Gueron M
Published: June 2011

A significant error may be introduced in intervals measured from the onset of the QRS if an electrocardiographic lead that does not record the earliest deflection is used. To ascertain to what extent the commonly used leads can be relied on to show the earliest QRS onset, 100 normal subjects and 219 patients with heart disease were studied by means of simultaneous recording of three leads: a right precordial lead chosen to show an rS configuration, lead II, and another limb lead chosen to show a qR configuration. Lead II most frequently showed a delayed QRS onset--in 34% of normal subjects and 36% of the patients. In the other limb lead the initial QRS deflection was delayed in 24% of the normal subjects and 23% of the patients. The QRS onset in the right precordial lead was never delayed in the normal subjects; however, it was delayed in this lead in 6% of the patients. The delays in each of the leads ranged from 5-20 msec. We conclude that while a right precordial lead is by far the most reliable single lead that can be used for interval measurements, simultaneous recording of a right precordial lead and a limb lead assures that recording of the earliest QRS onset in all cases.
Atrial excitability and conduction during rapid atrial pacing.
Authors: Plumb V J , Karp R B , James T N , Waldo A L
Published: June 2011

Using temporary atrial wire electrodes placed at selected atrial sites, rapid atrial pacing at rates of up to 368 beats/min was used to study atrial excitability and conduction in seven patients who underwent open heart surgery. The threshold for atrial pacing was found to be an exponential function of pacing rate (r = 0.55, p less than 0.01), increasing threefold when the fastest pacing rates were compared with the slowest pacing rates (p less than 0.005). Atrial conduction times (measured from pacing to recording sites), prolonged during rapid atrial pacing both for studies conducted before institution of cardiopulmonary bypass (p less than 0.005) and for those done 7 days postoperatively (p less than 0.05). However, prolongation of conduction times always depended on achievement of a critically rapid pacing rate. During rapid atrial pacing, we observed a high incidence of alternans of the atrial electrogram (17 of 42 studies). Thus, human atrial excitability, conduction and electrogram morphology are not constant during pacing at rapid rates. Rather, at rapid pacing rates, there is depression of atrial excitability, prolongation of atrial conduction times and alternation in electrogram morphology. These findings have clinical relevance and theoretical implications for the understanding and treatment of rapid atrial rhythms.
Strength-interval relations in a chronic canine model of myocardial infarction. Implications for the interpretation of electrophysiologic studies.
Authors: Michelson E L , Spear J F , Moore E N
Published: June 2011

Fifteen adult mongrel dogs underwent two-stage occlusion of the mid- or distal left anterior descending coronary artery and then a reperfusion stage. The dogs were studied 3-30 days later to determine strength-interval relations in a canine model of chronic myocardial infarction. These dogs were susceptible to the initiation of sustained ventricular tachyarrhythmias with the introduction of one, two or three ventricular extrastimuli. Using unipolar cathodal stimuli with a pulse width of 2 msec, strength-interval curves were constructed from measurements made at multiple sites in the distribution of occluded and nonoccluded vessels during drive pacing at a cycle length of 300 msec. At 56 normal sites, ventricular refractory periods measured at twice-diastolic-excitability threshold approximated the relative refractory periods (mean absolute difference 3 msec), but were variably longer than effective refractory periods (mean difference 18 msec, range 4-29 msec). At 51 infarct sites, differences between ventricular refractory periods measured at twice-diastolic-excitability threshold and both relative refractory periods (mean difference 13 msec, range -60 to +18 msec) and effective refractory periods (mean difference 28 msec, range 1-60 msec) were markedly disparate. These differences were further exaggerated after administration of i.v. procainamide. These findings suggest limitations in interpreting the results of programmed pacing studies performed using stimuli of twice-threshold intensity.
Atrial septal aneurysm: a cause for midsystolic click. Report of a case and review of the literature.
Authors: Alexander M D , Bloom K R , Hart P , D'Silva F , Murgo J P
Published: June 2011

A patient who was evaluated for a midsystolic click was found to have an aneurysm of the atrial septum as an isolated anomaly. Bulging of this aneurysm into the right atrium was associated with the production of the click. Echo-, phono-, and angiocardiographic features are presented, with a review of the literature on atrial septal aneurysms. These aneurysms, although rare, should be considered in the differential diagnosis of patients with midsystolic click.
Aortic input impedance in man: acute response to vasodilator drugs.
Authors: Gundel W , Cherry G , Rajagopalan B , Tan L B , Lee G , Schultz D
Published: June 2011

In 18 patients who underwent coronary arteriography, aortic velocity and pressure data were obtained during a control state and during either isoproterenol infusion at 1, 2 and 3 micrograms/min or graded nitroprusside infusion (average peak dose 60 micrograms/min). Impedance moduli and phase angles were derived to 10 Hz for controls states, isoproterenol at 2 micrograms/min, and at peak nitroprusside effect. Averaged control data included a mean resistance of 1460 dyn-sec-cm-5 and a characteristic impedance of 88 dyn-sec-cm-5 The characteristic impedance did not correlate with age (r = 0.21), coronary artery disease score (r = 0.17) or mean aortic pressure (r = -0.01). In 11 patients, isoproterenol induced a 38% reduction in mean resistance and a 10% reduction in mean aortic pressure. There was slight reduction in characteristic impedance and phase angles became less negative, to 2 Hz. In seven patients, nitroprusside induced a 38% reduction in mean resistance and a 22% reduction in mean aortic pressure. Impedance moduli decreased to 1.8 Hz and phase angles became less negative, to 3 Hz. Based on the different cardiovascular actions of these two drugs, the data suggest that vasodilators do not induce significant changes in the aortic impedance spectrum when not associated with a decrease in mean aortic pressure.
Effect of bypass surgery on survival in patients in low- and high-risk subgroups delineated by the use of simple clinical variables.
Authors: Detre K , Peduzzi P , Murphy M , Hultgren H , Thomsen J , Oberman A , Takaro T
Published: June 2011

A multivariate risk function was developed on data from all 508 medical patients in the Veterans Administration (VA) randomized study of coronary bypass surgery. The variables, in order of importance, were ST-segment depression on resting ECG, history of myocardial infarction, history of hypertension and New York Heart Association functional classification III or IV. These noninvasive variables have been reported to be risk factors in natural-history studies of coronary heart disease (CHD). Applying the risk function to medical and surgical patients of the 1972-1974 cohort yielded a 5-year probability of dying for each patient. Investigation of treatment effects in approximate terciles obtained by collapsing the probability distribution into low-, middle- and high-risk groups showed that surgery was beneficial for patients in the high-risk tercile even after removal of patients with left main coronary artery disease (17% surgical vs 34% medical mortality at 5 years; p less than 0.01). This finding was accentuated when patients in the 10 hospitals with the lowest operative mortality (3.3%) were compared. Mortality results in the low-risk tercile favored medical treatment (medical vs surgical mortality 7% vs 17%; p less than 0.05). The risk function predicted mortality well not only for te VA medical group, but also for an independent symptomatic CHD population from the University of Alabama arteriography registry. This report further delineates the advantages and limitations of coronary bypass surgery in CHD patients with chronic stable angina.
Size and motion of the mitral valve annulus in man. I. A two-dimensional echocardiographic method and findings in normal subjects.
Authors: Ormiston J A , Shah P M , Tei C , Wong M
Published: June 2011

Using wide-angle, phased-array, two-dimensional echocardiography, mitral leaflets and their annular attachments were recorded from a view close to the standard apical four-chamber view. The transducer was rotated and recordings were made at 30 degrees rotational intervals around the circumference of the mitral valve annulus. To reconstruct the annulus, the diameters (chords) from each rotational interval were arranged around a reference point. This was done for 12 times during the cardiac cycle. Annular areas were planimetered and circumferences measured. Correlation was good for areas reconstructed and measured by the same observer on separate occasions (r = 0.963) and by two different observers (r = 0.987). In 11 normal subjects the annular area index (area divided by body surface area) increased during diastole to a maximum of 3.8 +/- 0.7 cm2/m2 (mean +/- SD) in late diastole. There was presystolic followed by systolic narrowing to a minimum in midsystole. The mean reduction in area was 26 +/- 3%. The maximal annular circumference was 9.3 +/- 0.9 cm and the mean reduction in circumference was 13 +/- 3%. The overall motion pattern was similar to that reported in experimental studies in the dog. Mitral annular reconstruction may provide new information about normal and abnormal function of the mitral valve apparatus.
Acute effects of oral pirbuterol on myocardial oxygen metabolism and systemic hemodynamics in chronic congestive heart failure.
Authors: Rude R E , Turi Z , Brown E J , Lorell B H , Colucci W S , Mudge G H , Taylor C R , Grossman W
Published: June 2011

Pirbuterol hydrochloride, an orally effective beta-adrenergic agonist, improves hemodynamic abnormalities in patients with congestive heart failure, but its effects on myocardial oxygen consumption (MVO2) and coronary blood flow have not been characterized. We studied the effects of 20-30 mg of oral pirbuterol on myocardial metabolic and hemodynamic parameters in 12 patients (six with coronary artery disease) with chronic CHF refractory to standard medical therapy. Pirbuterol induced an increase in cardiac index (1.7 +/- 0.1 to 2.3 +/- 0.2 l/min/m2, p less than 0.05) and a fall in systemic vascular resistance (1884 +/- 118 to 1391 +/- 69 dyn-sec-cm-5, p less than 0.01) 2 hours after administration. Pulmonary capillary wedge pressure fell from arterial and right atrial pressures did not change. Heart rate remained constant. Arterial-coronary sinus oxygen content difference narrowed (from 12.9 +/- 0.4 to 11.1 +/- 0.3 vol%, p less than 0.05), while no significant change occurred in MVO2. Myocardial oxygen extraction ratio and myocardial lactate extraction ratio did not change, and no patient developed angina or electrocardiographic evidence of myocardial ischemia. Patients with coronary artery disease had hemodynamic and myocardial metabolic responses similar to those without coronary artery disease. Pirbuterol effects substantial acute hemodynamic improvement in patients with chronic congestive heart failure without increasing requirements for coronary blood flow or myocardial oxygen delivery and without provoking myocardial ischemia.
Radiation exposure to the child during cardiac catheterization.
Authors: Waldman J D , Rummerfield P S , Gilpin E A , Kirkpatrick S E
Published: June 2011

Few data are available regarding radiation exposure to children during cardiac catheterization. Using lithium fluoride thermoluminescent dosimeters, radiation exposure was measured during precatheterization chest roentgenography, fluoroscopy (hemodynamic assessment phase of catheterization) and cineangiography in 30 infants and children, ages 3 days to 21 years. Dosimeters were placed over the eyes, thyroid, anterior chest, posterior chest, anterior abdomen, posterior abdomen and gonads. Average absorbed chest doses were 24.5 mR during chest roentgenography, 5810 mR during catheterization fluoroscopy and 1592 mR during cineangiography. During the complete catheterization, average doses were 26 mR to the eyes, 431 mR to the thyroid area, 150 mR to the abdomen and 11 mR to the gonads. Radiation exposure during pediatric cardiac catheterization is low to the eyes and gonads but high to the chest and thyroid area. To decrease radiation dosage we suggest (1) low pulse-rate fluoroscopy; (2) substitution of contrast echocardiography for cineangiography; (3) large-plate abdominal/gonadal shielding; (4) a selective shield for thyroid area; (5) a very small field during catheter manipulation. Minimum radiation consistent with accurate diagnosis is optimal; however, erroneous or incomplete diagnosis is more dangerous than radiation-related hazards.
Concealed ventricular parasystole uncovered in the form of ventricular escapes of variable coupling.
Authors: Nau G J , Aldariz A E , Acunzo R S , Chiale P A , Elizari M V , Rosenbaum M B
Published: June 2011

Exit block from a parasystolic focus is recognized when automatic discharges fail to become manifest during the excitable phase of the ventricular cycle. In the present study, an apparently complete exit block and a persistently concealed ventricular parasystole (VP) resulted from an exit refractory period (ExRP) longer than the sinus cycle length. Slowing of the heart rate caused the concealed VP to become apparent in the form of ventricular escapes of variable coupling and as an idioventricular rhythm that failed to show initial "warming up." These features reflect the fact that the automatic focus is protected from activity of the sinus impulses, which, however, can induce a prolonged ExRP. Seven cases of concealed VP are discussed. In two, concealment occurred spontaneously during the follow-up of a typical VP; in three, it was provoked by conduction-depressing drugs; and in two, ventricular escapes of varying coupling were shown to represent the manifestation of a concealed and previously unrecognized VP. In two cases, isoproterenol caused reappearance of typical VP, probably through a shortening of the ExRP. While isoproterenol may be useful for uncovering a concealed VP, conduction-depressing drugs may be used to provoke or increase exit block. Total extinction of the VP seemed to occur in two patients during follow-up studies.
Effect of increased adrenergic activity on the relationship between electrical and mechanical systole.
Authors: Boudoulas H , Geleris P , Lewis R P , Leier C V
Published: June 2011

The effect of catecholamines and atrial pacing on the relationship between electrical systole (QT) and mechanical systole (QS2) was studied in 12 normal subjects and in 32 patients. The studied subjects were divided into three groups. Group 1 included 12 normal subjects in whom serial isoproterenol infusions were performed before and after oral propranolol administration, 160 mg daily for 2 days. During the 24-hour control period, the QT was always shorter than the QS2 (from 14 +/- 3 to 19 +/- 4 msec, p less than 0.01), while during isoproterenol infusion the QT was always greater than the QS2 (from 28 +/- 5 to 34 +/- 5 msec, p less than 0.01). Group 2 included 26 patients in whom 24-hour urinary epinephrine (E) and norepinephrine (NE) were measured the same day as systolic time interval measurements. The E + NE was higher in patients in whom the QT was longer than the QS2 compared with patients in whom the QT was the same or shorter than QS2 (107 +/- 9 vs 61 +/- 7 microgram/24 hours, p less than 0.05). Group 3 included six patients in whom the heart rate was increased with atrial pacing, from 80 to 130 beats/min. The QT was always shorter than the QS2 (from 13 +/- 3 to 24 +/- 5 msec, p less than 0.01). Adrenergic stimulation results in a relative prolongation of the QT with the QS2 shortening and the QT remaining unaffected. The QT is normally shorter than the QS2, so the duration of QT should always be considered in relationship to the duration of QS2. Finally, a reversal of the normal QT-Qs2 relationship may provide a simple index of increased adrenergic activity.
Effect of myocardial infarction on high-frequency QRS potentials.
Authors: Goldberger A L , Bhargava V , Froelicher V , Covell J
Published: June 2011

Studies have shown that the number of high-frequency QRS notches increases after myocardial infarction (MI). To assess overall high-frequency (greater than 80 Hz) potentials more quantitatively, we adapted filtered and the root-mean-square (RMS) voltage of the residual (80-300 Hz) signal computed. High-frequency RMS values were significantly (p less than 0.01) greater in leads II, III and aVf in normal subjects (n = 12) than in patients with inferior infarction (n = 12). Similarly, high-frequency RMS values were higher (p less than 0.01) in leads V2 and V5 in normal subjects (n = 14) than in patients with prior anterior MI (n = 14). A reduction in high-frequency RMS values with inferior infarction was independently confirmed using Fourier analysis of the QRS in lead II. QRS notching in these subjects was also quantified by computing the number of baseline crossings of the first derivative (dV/dt). As predicted, notching was significantly greater (p less than 0.05) both with inferior MI (lead II) and anterior MI (lead V5). However, contrary to classic theory, the number of notches correlated negatively with direct measurements of high-frequency RMS voltage in lead II (r = -0.63) and lead V5 (r = -0.49). Positive correlations were obtained between high-frequency potentials and two new indexes that measure the amplitude of QRS dV/dt-peak-to-peak amplitude of dV/dt and RMS dV/dt. Using these indexes, absolute separation of inferior MI patients and normal subjects was obtained. We conclude that MI increases low-amplitude QRS notching but diminishes total high-frequency voltage, probably because of an overall decrease in electromotive potentials and slowing of ventricular conduction.
Acute arterial hypertension during spontaneous angina in patients with fixed coronary stenosis and exertional angina: an associated rather than a triggering phenomenon.
Authors: Figueras J , Cinca J
Published: June 2011

The role of systemic arterial hypertension as a possible trigger of myocardial ischemia during angina at rest was studied in 13 consecutive patients who also had a history of exertional angina. Significant (greater than or equal to 70%) stenosis of at least one major vessel was present in each of the 10 patients in whom coronary arteriography was carried out. After documentation of the electrocardiographic and arterial blood pressure changes during two or more episodes of resting angina, i.v. methoxamine was infused under continuous monitoring of the ECG, arterial blood pressure and pulmonary artery diastolic pressure. The heart rate was maintained either spontaneously or by atrial pacing to levels similar to those during angina at rest. Despite increases in arterial blood pressure and the double product (systolic blood pressure x heart rate) to levels higher than those during spontaneous angina in all patients, no chest pain or electrocardiographic changes occurred in nine patients. In the other four patients, however, angina supervened. Three of these four patients, but only one of the remaining nine, had a borderline or elevated pulmonary artery diastolic pressure at rest. We conclude that in a considerable number of patients with "nonvariant" resting angina, acute increases in arterial blood pressure during the spontaneous attacks are not likely to be the cause of myocardial ischemia. Nevertheless, in some of these patients, increases in resting pulmonary artery diastolic pressure may favor the development of ischemia during afterload augmentation.
Patterns of disturbed myocardial perfusion in patients with coronary artery disease. Regional myocardial perfusion in angina pectoris.
Authors: Selwyn A P , Forse G , Fox K , Jonathan A , Steiner R
Published: June 2011

Fifty patients who presented with angina pectoris were studied to examine the disturbances of regional myocardial perfusion during stress. Each patient underwent 16-point precordial mapping of the ECG during an exercise test, and coronary and left ventricular angiography. Regional myocardial perfusion was assessed using an atrial pacing test and a short-lived radionuclide, krypton-81m. Eleven patients had negative exercise tests and uniform increases in myocardial activity of krypton-81m of 98 +/- 18.0% during pacing. Ten patients performed 30,000-43,000 J in positive exercise tests. These patients showed abnormal coronary anatomy and increases in myocardial activity of krypton-81m to remote and jeopardized myocardium at the onset of pacing. However, further pacing produced a decrease in activity in the affected segment of 68.0 +/- 9.0% accompanied by ST-segment depression and angina. Twelve patients achieved 26,000-32,000 J in positive exercise tests and had significant coronary artery disease. Atrial pacing produced increased activity of krypton-81m to remote myocardium. The jeopardized segment at first showed no change and then a decrease in regional activity of krypton-81m (89.0 +/- 17%) accompanied by ST-segment depression and chest pain. Seventeen patients achieved only 7000-22,000 J in positive exercise tests. These patients showed abnormal coronary anatomy and developed decreases in regional activity of krypton-81m to the affected segment of myocardium starting at the onset of atrial pacing and decreasing by 88 +/- 0 7.0% below control. We conclude that different patterns of disturbed myocardial distribution of krypton-81m are present during stress-induced ischemia in patients with coronary artery disease. There was a close temporal relationship between these disturbances and ST-segment depression.
Electrophysiologic and histologic correlations in chronic complete atrioventricular block.
Authors: Ohkawa S , Sugiura M , Itoh Y , Kitano K , Hiraoka K , Ueda K , Murakami M
Published: June 2011

Electrophysiologic studies using the His bundle electrogram (HBE) and histologic studies of serial sections of the conduction system were correlated in two groups of deceased patients. Group 1 consisted of five patients with chronic complete atrioventricular block (CAVB) who had narrow QRS complexes and AH block (block proximal to the His bundle deflection). Group 2 consisted of four patients with chronic CAVB who had wide QRS complexes and HV block (block distal to the His bundle deflection). In group 1, the sites of the main lesion were not located in the approaches to the atrioventricular (AV) node or the AV node, but were found in the penetrating portion of the His bundle in one patient and in the branching portion of the His bundle in three patients. In the remaining patient, the main site of block could not be demonstrated histologically in the AV conduction system, but marked fibrosis of the approaches to the sinoatrial node and surrounding atrial muscle was found. In all patients of group 2, the site of the main lesion was located in the bilateral bundle branches, and thus was compatible with so-called trifascicular block. This correlation study between the His bundle electrogram and histologic findings of the AV conduction system showed that in some cases, CAVB presenting as AH block on the HBE can be associated with a lesion in the branching portion of the His bundle (distal His), and that CAVB presenting as HV block on the HBE is associated with a bilateral lesion of the bundle branches.
Lead systems for internal ventricular fibrillation.
Authors: Deeb G M , Griffith B P , Thompson M E , Langer A , Heilman M S , Hardesty R L
Published: June 2011

We examined the feasibility of using a standby automatic implantable defibrillator and established thresholds for internal defibrillation. The implantable defibrillator senses ventricular fibrillation and delivers an electrical impulse for defibrillation. Two lead systems for the device have been investigated. System I consists of two 12-cm2 silicone-covered titanium mesh patches attached to the atrial and diaphragmatic pericardial surfaces. System II has an identical diaphragmatic patch and a titanium spring catheter, with a 12-cm2 surface area of conductivity, placed transvenously in the right atrium. Both systems were implanted by thoracotomy in 12 dogs (mean weight 20 kg) and by a subxiphoid approach in 10 pigs (mean weight 20 kg). The defibrillation threshold (lowest energy required for 80% success) was determined periodically for 54 weeks in the dogs (615 trials) and at 6 weeks for the pigs (100 trials). In dogs, the mean defibrillation threshold with system I leads at 4 weeks was 10.5 J and did not change significantly over a 54-week period (p greater than 0.05). Similar results were obtained in the pig at 4 weeks. The defibrillation thresholds for both lead systems in dogs and pigs using a transpleural thoracotomy or a subxiphoid approach are satisfactory for an implantable defibrillator that produces 20-35 J.
Cardiac infarction injury score: an electrocardiographic coding scheme for ischemic heart disease.
Authors: Rautaharju P M , Warren J W , Jain U , Wolf H K , Nielsen C L
Published: June 2011

A multivariate decision-theoretic electrocardiogram (ECG) classification scheme called Cardiac Infarction Injury Score (CIIS) was developed using ECGs of 387 patients with myocardial infarction (MI) and 320 subjects without infarction. The most accurate and stable classification was achieved by using a combination of eight binary (single threshold), three ternary (two thresholds), and four ECG features measured on a continuous scale. For practical visual coding of ECGs, the CIIS coding procedure uses a checklist containing 12 items measured from the conventional 12-lead ECG. The CIIS test results indicate that, in comparison with conventional ECG criteria for MI used in clinical trials, the diagnostic accuracy can be considerably improved by optimizing feature and threshold selection and by multivariate analysis. The CIIS detected MI with a sensitivity of 85% and a specificity of 95%. Using a higher severity level, a specificity of 99% was achieved, with a sensitivity of 71%. One of the primary uses of the CIIS is coding of significant worsening of the ECG with new coronary events from annually recorded ECGs in clinical trials and epidemiologic studies.
Effects of isoproterenol on bradycardia-dependent intra-His and left bundle branch blocks.
Authors: Suárez L D , Kretz A , Alvarez J A , Martinez J M , Perosio A M
Published: June 2011

The electrophysiologic study of a patient with a history of fainting showed first- and second-degree Mobitz type I intraatrial and intra-His (IH) bundle blocks. Tachycardia and bradycardia-dependent IH block and bradycardia-dependent left bundle branch block were also present. Bradycardia-dependent block was probably caused by slight hypopolarization plus a slow rising slope of phase 4 depolarization and a shift of the threshold potential toward zero. Two months later a second electrophysiologic study was performed before, during and after administration of i.v. isoproterenol (IP). Shortening of atrium-His (AH1) and IH (H1H2) conduction time during faster heart rates caused by IP infusion may be related to its hyperpolarizing effect. Simultaneously, a shifting to the left of both bradycardia-dependent IH and left bundle branch block ranges was recorded during vagally induced cardiac slowing. These findings suggest that IP produces an increase in the slope of phase 4 depolarization of the His bundle and left bundle branch fibers and a simultaneous and concordant effect at both levels of the intraventricular conduction system.
Experimental study of afterload-reducing therapy: the effects of the reduction of systemic vascular resistance on cardiac output, aortic pressure and coronary circulation in isolated, ejecting canine hearts.
Authors: Isoyama S , Maruyama Y , Koiwa Y , Ishide N , Kitaoka S , Tamaki K , Sato S , Shimizu Y , Ino-Oka E , Takishima T
Published: June 2011

The relationship between cardiac output (CO) and peripheral resistance (Rp) was examined under the following conditions for coronary perfusion: constant coronary flow perfusion; perfusion with a pressure equal to mean aortic pressure (AoP perfusion); and perfusion with a pressure equal to the mean AoP - 30 mm Hg (AoP - 30 mm Hg perfusion). We also examined the coronary pressure-flow relationship. For these studies, we used paced, isolated, ejecting canine hearts, which were loaded by a hydraulic system that simulated the input impedance of a dog's systemic arterial tree. The CO in the constant coronary flow perfusion continued to increase with the reduction of Rp. The CO in the AoP perfusion became maximal at a slightly subphysiologic Rp, or at an average mean AoP of 65 mm Hg. This mean AoP was closely associated with the lower limit of the autoregulation of coronary blood flow. In the AoP - 30 mm Hg perfusion, the mean AoP at which CO became maximal was 72 mm Hg and the corresponding coronary perfusion pressure appeared to be lower than the lower limit of the perfusion pressure range for coronary flow autoregulation. The Rp value at that point was slightly higher than the physiologic range. We conclude that when coronary perfusion pressure changes with mean AoP, and when left ventricular end-diastolic pressure is fixed, there is a clear optimal Rp at which CO becomes maximal, and this optimal Rp is higher if coronary perfusion pressure is biased from mean AoP to a significant degree.
Sensitivity and specificity of hemodynamic criteria in the diagnosis of acute right ventricular infarction.
Authors: Lopez-Sendon J , Coma-Canella I , Gamallo C
Published: June 2011

To test the sensitivity and specificity of hemodynamic criteria for acute right ventricular infarction (RVI), two groups of patients with anatomically proved acute myocardial infarction and hemodynamic monitoring were studied. Group A included 22 patients acute RVI and group B, 38 with infarction confined to the left ventricle. In both groups, the closest relation between right atrial and pulmonary capillary pressures (RAP and PCP), as well as the presence of a severe noncompliant pattern (SNCP), were studied. A SNCP was defined as a y descent deeper than the x descent in RAP. RAP was equal to or higher than PCP in 10 patients from group A and in none from group B. In group B, a significant relation was found between RAP and PCP (r = 0.777, y = 0.43x + 0.18) (p less than 0.05), and the 95% confidence limits could be calculated. Above these limits, a closer relation between RAP and PCP was only found in patients with RVI. However, six patients with RVI showed an RAP/PCP relation within 95% confidence limits of group B (sensitivity 72.7%, specificity 100%). A SNCP was present in 12 patients with RVI and only in one without RVI (p less than 0.01) (sensitivity 54.5% and specificity 97.4%). When either criterion is present (close relation between RAP and PCP or SNCP), a high sensitivity (81.8%) and specificity (97.4%) can be achieved in the diagnosis of acute RVI.
Tetralogy of Fallot: an angiographic-pathologic correlative study.
Authors: Soto B , Pacifico A D , Ceballos R , Bargeron L M
Published: June 2011

The anatomic abnormalities observed by cineangiographic axial techniques of 12 patients with tetralogy of Fallot were correlated with anatomic details noted at necropsy. Right ventricular angiograms made in the right anterior oblique view best demonstrated the severity and type of infundibular obstruction and also permitted differentiation of the perimembranous, infundibular muscular and subarterial types of ventricular septal defects. The degree of aortic overriding was best displayed in the long-axis view. Comparison of the intracardiac anatomy of each postmortem specimen with the respective premortem cineangiogram has provided further clarification of the angiographic anatomy displayed by these axial techniques.
A comparison of coarctation resection and patch angioplasty using postexercise blood pressure measurements.
Authors: Connor T M , Baker W P
Published: June 2011

Postexercise arm-to-leg blood pressure gradients were measured in 31 patients to determine the effectiveness of two surgical techniques for treating coarctation of the aorta. The arm-to-leg postexercise mean systolic blood pressure gradient was 29 mm Hg lower in 13 patients treated with Dacron patch angioplasty than in 18 patients whose coarctation was resected (p less than 0.01). Some patients with high postexercise gradients after coarctation resection had a reduced proximal aortic lumen by angiography. The results of this study indicate that Dacron patch angioplasty is the method of choice for effectively reducing postexercise systolic pressure gradients in patients with coarctation and hypoplasia of the aortic isthmus.
Agreement in human interpretation of analog thallium myocardial perfusion images.
Authors: Atwood J E , Jensen D , Froelicher V , Witztum K , Gerber K , Gilpin E , Ashburn W
Published: June 2011

To assess the agreement of human interpretation of analog thallium myocardial perfusion images, four experienced interpreters evaluated 100 images on two occasions using a form designed to limit reader variability. A high intraobserver agreement (agreement by same observer at separate times) of 89--93% was found when films were interpreted as normal or abnormal (a dichotomous decision). Interobserver agreement for a majority grouping of observers (three or four) was 75% for an abnormal and 68% for a normal interpretation. However, agreement ranged from 11--79% when interpreters were asked to read the anatomic location of defects. Posterior and lateral wall defects were interpreted with the least amount of agreement. These results indicate that caution must be taken when interpreting defect location. Using a scale of 1--10 to grade the severity of a defect, correlations of 0.82--0.86 were found when reading defects in the lateral and anterior projections. Higher correlations, from 0.86--0.94, were found in left anterior oblique views. Use of reporting forms with specific criteria, multiple observers at one occasion, and/or computer processing may improve agreement. A brief review of the agreement of cardiology testing procedures is also presented.
Are clinical trials in coronary heart disease oversold or undersold?
Authors: Detre K M , Ware J , Mantel N
Published: June 2011

Randomized clinical trials constitute the formal experiments in therapeutics. Many such trials in coronary heart disease have terminated inconclusively or in controversy. In this editorial, we analyze some of the methodologic issues that may lead to controversy; the main reason for the low success rate may lie in insufficient understanding of the complex biology of the disease and in failure to select the appropriate models for therapy. We argue that these difficulties only strengthen the need for the rigorous experimental approach to the evaluation of therapies for coronary heart disease.
Relationship between changes in left ventricular inotropic state and relaxation in normal subjects and in patients with coronary artery disease.
Authors: Rousseau M F , Pouleur H , Detry J M , Brasseur L A
Published: June 2011

The aim of the study was to examine the changes in left ventricular (LV) relaxation rate induced by variations in inotropic state. Eight normal subjects and 29 patients with coronary artery disease (CAD) were studied. First, we used interventions that increase myocardial calcium influx (atrial pacing or postpacing beat) or decrease it (intracoronary injection of nifedipine). Relaxation rate was estimated from the time constant (T1) of isovolumic LV pressure fall during the fist 40 msec after peak negative dP/dt. Under basal conditions, T1 was impaired in CAD patients (58 vs 43 msec; p less than 0.01), despite similar heart rate, LV pressures and peak positive dP/dt (1620 vs 1787 mm Hg/sec; NS). During atrial pacing at 135 +/- 7 beats/min, peak positive dP/dt increased to 2220 mm Hg/sec in 11 CAD patients and to 2256 mm Hg/sec in eight normal subjects. T1 decreased more in CAD patients than in normal subjects (17 vs 7 msec; p less than 0.01). T1 changes also differed in the postpacing beat between CAD patients and normal subjects (-6 vs 5 msec; p less than 0.01) or when nifedipine was injected during the pacing (4 vs 20 msec; p less than 0.01). Intravenous calcium injection during atrial pacing in another group of 18 CAD patients further improved peak positive dP/dt and T1 (-3 msec; p less than 0.05) and normalized the changes in relaxation during the postpacing heart. Our data indicate that a variable coupling between LV inotropic state and relaxation rate exists in man during changes in calcium influx and that this coupling is abnormal in CAD patients.
A new, simplified and accurate method for determining ejection fraction with two-dimensional echocardiography.
Authors: Quinones M A , Waggoner A D , Reduto L A , Nelson J G , Young J B , Winters W L , Ribeiro L G , Miller R R
Published: June 2011

A new method to determine left ventricular (LV) ejection fraction (EF) with wide-angle, two-dimensional echocardiography (2-D echo) has been developed using the parasternal long-axis, apical four-chamber and apical long-axis views. End-diastolic and end-systolic measurements of LV short axes at the base and mid-LV cavity in the parasternal long-axis view and at the upper, middle and lower thirds of the cavity in the apical views are made, from which an averaged minor axis at end-diastolic and at end-systole is calculated. Fractional shortening of the LV long axis (delta L) is estimated from apical contraction. Satisfactory 2-D echoes were obtained in 55 of 58 nonselected patients (all three views in 32 patients, two views in 22 and one view in one); 42 of 55 patients had coronary artery disease. EF by 2-D echo was compared with EF by gated cardiac blood pool imaging in all patients (r = 0.927, SEE = 6.7%) and to EF by single-plane cineangiography (angio) in 35 of 55 patients (r = 0.913, SEE = 7.4%). LV dyssynergy was frequently present and involved the apex in 29 of 55 patients. Using angio as the standard for evaluating wall motion at the apex, 2-D echo was 100% sensitive and specific in detecting abnormal apical wall motion. We conclude that EF can be determined accurately with 2-D echo in a large group of patients with and without dyssynergy by a simple method that eliminates the need for planimetry or computer assistance.
Acute and chronic treatment of severe and malignant hypertension with the oral angiotensin-converting enzyme inhibitor captopril.
Authors: Case D B , Atlas S A , Sullivan P A , Laragh J H
Published: June 2011

The patients with severe and 10 with accelerated or malignant hypertension were treated with the angiotensin-converting enzyme inhibitor captopril. Captopril acutely reduced blood pressure in all patients except two who had suppressed plasma renin activity. Four patients with encephalopathy showed immediate improvement after the first dose. Two patients could be withdrawn from nitroprusside infusion upon administration of captopril. Nineteen of 20 patients have remained on captopril for 12-32 months. Blood pressure is controlled in 18 and improved in two. Eleven required addition of diuretic and one addition of clonidine. The maximal antihypertensive effect of captopril with or without diuretics was evident after 3 months of continuous therapy and was associated with elevated plasma renin levels, normal aldosterone excretion and preservation of renal function. Captopril was well-tolerated, but produced occasional rash, loss of taste and proteinuria. We conclude that captopril, alone or in combination with other drugs, is effective in both the acute and long-term management of severe and malignant hypertension.
Congenital coronary artery obstruction associated with aortic anomalies in children: report of two cases.
Authors: Gibson R , Nihill M R , Mullins C E , Cooley D A , Sandiford F M , McNamara D G
Published: June 2011

Coronary arterial obstruction associated with congenital aortic valve disease is rare in children. We studied two children with aortic valve disease and symptoms of coronary insufficiency. Cineangiography revealed localized obstruction of the proximal left coronary artery. In one patient, a membrane-like structure partially covered the left sinus of Valsalva, almost isolating the ostium of the left coronary artery; the other patient had severe stenosis of the proximal left coronary artery and a congenitally hypoplastic left coronary cusp. Surgical repair was successful in both cases. Symptoms of myocardial ischemia in children with aortic valve disease should be investigated promptly to exclude obstruction of the coronary arteries.
Histocompatibility antigens in black patients with essential hypertension.
Authors: Patel R , Johnson J
Published: June 2011

Essential hypertension is a common disorder with potentially life-threatening sequelae. Hypertension among black persons may have characteristics different from hypertension among white persons. It has been estimated that up to 60% of population variance in blood pressure may be attributable to genetic differences. We studied the distribution of HLA antigens in 100 black hypertensives and 100 normotensive controls. Hypertension was not significantly associated with any of the 25 HLA antigens identified. We conclude that HLA-A and HLA-B locus antigens are not associated with essential hypertension in the black patient.
Prevention of chronic canine ventricular tachyarrhythmias with bretylium tosylate.
Authors: Patterson E , Gibson J K
Published: June 2011

The ability of chronic bretylium tosylate treatment to prevent the induction of ventricular tachycardia was assessed in the conscious dog subjected to serial programmed ventricular stimulation on days 3-6 after acute myocardial infarction. In 34 untreated control dogs, programmed ventricular stimulation produced nonsustained ventricular tachycardia in 11 dogs (32%), sustained ventricular tachycardia in 10 (29%), and ventricular fibrillation in 10 (29%) on the third and fourth day after occlusion and reperfusion of the left anterior descending coronary artery. Bretylium tosylate, 5 mg/kg i.v., was given every 12 hours to a separate group of seven dogs after the induction of ischemic myocardial injury. Programmed ventricular stimulation on the third and fourth days after the induction of myocardial ischemic injury failed to elicit ventricular arrhythmias. Induction of arrhythmias by programmed electrical stimulation could be induced in each of the seven dogs; however, 36 hours after discontinuing bretylium tosylate, two dogs (29%) had non-sustained ventricular tachycardia and five (71%) had sustained ventricular tachycardia. When retested at 60 hours after withdrawal of bretylium tosylate, five (71%) had sustained ventricular tachycardia and two (28%) developed ventricular fibrillation. Readministration of bretylium tosylate (5 mg/kg, i.v.) to four of the five surviving dogs prevented the induction of ventricular arrhythmias in response to programmed ventricular stimulation. The results of these investigations suggest that bretylium tosylate may be effective in preventing the onset of reentrant ventricular rhythms after myocardial ischemic damage, and therefore may be of value in preventing sudden coronary death.
Interventricular septal motion: biventricular angiographic assessment of its relative contribution to left and right ventricular contraction.
Authors: Banka V S , Agarwal J B , Bodenheimer M M , Helfant R H
Published: June 2011

The interventricular septum (IVS) has conventionally been regarded as a functional part of the left ventricle (LV). To determine its normal range of motion, simultaneous biventricular cineangiograms (60 frames/sec) were performed (60 degrees left anterior oblique) in nine subjects without coronary or other heart disease. Arrhythmias were avoided by using a specially designed right ventricular (RV) angiographic catheter. IVS motion was studied qualitatively by three observers and quantitatively by superimposing end-systolic and diastolic frames using intra- and extracardiac reference points. Two transverse chords that trisected the end-systolic length of the IVS were drawn to quantitate IVS, LV and RV free wall motion. Qualitatively, the IVS thickened toward both RV and LV cavities as a result of shortening on its longitudinal axis. LV motion was 39.9 +/- 7.2% on the transverse axis, of which 31.2 +/- 5.2% was contributed by the LV free wall and 8.5 +/- 2.1% by IVS. RV transverse axis motion was 36.9 +/- 3.7%, of which 28.6 +/- 2.1% was contributed by the RV free wall and 8.3 +/- 2.3% by IVS motion. There was no difference between IVS motion toward the LV and that toward the RV. The IVS longitudinal axis shortened by 17.4 +/- 2.8% (p less than 0.001). The mean systolic IVS thickness increased symmetrically from 7.43 +/- 0.55 mm to 12.49 +/- 0.39 mm (p less than 0.001). In brief, the IVS thickens on its transverse axis and shortens on its longitudinal axis, contributing equally to RV and LV function.