John R. Blackmon

Quantitative Angiocardiography I. The Normal Left Ventricle in Man

Quantitative angiocardiography has been utilized to study the left ventricle of seven women and 15 men who had no evidence of heart disease. The left ventricular enddiastolic volume, end-systolic volume, and stroke volume were calculated in 15 individuals and left ventricular mass was determined in all 22 subjects. The mean end-diastolic volume was 70 cc/m.2 The left ventricular wall thickness during diastole averaged 8.9 mm for women and 11.9 mm for men and the mean left ventricular mass was 76 g/m2 for women and 99 g/m2 for men. The ventricular volumes did not correlate well with age, sex, body surface area, or weight, but correlated in a negative manner with heart rate. There was a significant difference between left ventricular wall thickness and mass in normal men and women. Values for normal left ventricular volumes obtained by other investigators using angiocardiographic and indicator-dilution methods are compared with the results of this study. The values obtained for left ventricular mass by the angiocardiographic method used in this study are similar to those obtained by other investigators in postmortem hearts.

MYOCARDIAL ISCHEMIA AFTER MAXIMAL EXERCISE IN HEALTHY MEN. A METHOD FOR DETECTING POTENTIAL CORONARY HEART DISEASE

Abstract A study of 433 asymptomatic men emphasizes the value of strenuous exercise testing in the early detection of myocardial ischemia. The sensitivity of the maximal exercise capacity test was nine times greater than that of the double Masters two-step test in eliciting electrocardiographic evidence of myocardial ischemia in 201 “normal” men who were over 34 years of age. Improved detection of potential coronary heart disease by this method is illustrated by comparison with several epidemiologic studies. If the reliability and specificity of this electrocardiographic abnormality in predicting clinical coronary heart disease is confirmed by future follow-up examinations, a method of detection and study of potential coronary heart disease and factors influencing its course will be available.

Disparities Between Aortic and Peripheral Pulse Pressures Induced by Upright Exercise and Vasomotor Changes in Man

Blood pressures were recorded simultaneously from the aortic arch and radial artery using two manometric systems with identical static and dynamic sensitivities. Measurements were made in four normal young men at rest and upright exercise requiring 29, 49, 78, and 100% of maximal oxygen uptake. Average radial arterial pressure rose from 133/66 mm Hg at rest to 236/58 mm Hg at maximal exercise. At the same time, average aortic pressures were 112/68 and 154/70 mm Hg, respectively. From rest to maximal exercise, pulse pressures at central and peripheral sites increased by factors of 1.95 and 2.60, respectively. Inducing reactive hyperemia in the arm abolished peripheral amplification. This amplification also diminished with time during prolonged heavy exercise. Mean pressures were nearly identical at the two sites at any oxygen uptake; mean pressures rose from 87 to 104 mm Hg from mild to maximal exercise. We conclude that estimates of stress on aortic and cerebral vessel walls and central baroreceptors would be grossly overestimated by use of peripheral pulse pressures.

The Wolff-Parkinson-White syndrome: problems in evaluation and surgical therapy.

Two patients with WPW syndrome underwent surgery to ablate accessory conduction pathways. Endocardial and epicardial mapping in both patients had indicated an area of early right ventricular depolarization. Surgical transection of the areas of early depolarization failed in both cases to normalize the electrocardiogram. In the first patient, additional resection in the area of the A-V node failed to produce heart block and the ECG remained abnormal. However, the paroxysmal tachycardia ceased, and she has remained asymptomatic and active 12 months after surgery. In the second patient, as the A-V node was about to be sectioned, pressure and procaine near the A-V node caused the ECG to normalize transiently and after resection permanently. Microscopic study of this tissue showed “P cells.” Postoperatively the patient demonstrated normal A-V nodal function. He was discharged with a normal ECG but expired soon after discharge. Postmortem examination of the heart demonstrated the A-V node and bundle of His plus the location of the resection adjacent to the bundle of His. These two cases illustrate disparities between electrophysiologic mapping and actual site of the accessory conduction pathway. In one of the cases an accessory bundle was demonstrated histologically.

History and physical examination in acute pulmonary embolism in patients without preexisting cardiac or pulmonary disease

The history and physical examination were assessed in 215 patients with acute pulmonary embolism uncomplicated by preexisting cardiac or pulmonary disease. The patients had been included in the Urokinase Pulmonary Embolism Trial or the Urokinase-Streptokinase Embolism Trial. Presenting syndromes were (1) circulatory collapse with shock (10 percent) or syncope (9 percent); (2) pulmonary infarction with hemoptysis (25 percent) or pleuritic pain and no hemoptysis (41 percent); (3) uncomplicated embolism characterized by dyspnea (12 percent) or nonpleuritic pain usually with tachypnea (3 percent) or deep venous thrombosis with tachypnea (0.5 percent). The most frequent symptoms were dyspnea (84 percent), pleuritic pain (74 percent), apprehension (63 percent) and cough (50 percent). Hemoptysis occurred in only 28 percent. Dyspnea, hemoptysis or pleuritic pain occurred separately or in combination in 94 percent. All three occurred in only 22 percent. The most frequent signs were tachypnea (respiration ate 20/min or more) (85 percent), tachycardia (heart rate 100 beats/min or more) (58 percent), accentuated pulmonary component of the second heart sound (57 percent) and rales (56 percent). Signs of deep venous thrombosis were present in only 41 percent and a pleural friction rub was present in only 18 percent. Either dyspnea or tachypnea occurred in 96 percent. Dyspnea, tachypnea or deep venous thrombosis occurred in 99 percent. As a group, the identified clinical manifestations, although nonspecific, are strongly suggestive of acute pulmonary embolism. Conversely, acute pulmonary embolism was rarely identified in the absence of dyspnea, tachypnea or deep venous thrombosis.

Quantitative Angiocardiography III. Relationships of Left Ventricular Pressure, Volume, and Mass in Aortic Valve Disease

Quantitative angiocardiographic techniques have been used to determine left ventricular volume and mass in 100 patients with isolated aortic valve disease. The patients were divided into three groups: aortic stenosis (AS), 22 patients; aortic regurgitation (AR), 38 patients; and combined stenosis and regurgitation (AS+AR), 40 patients. The distribution of left ventricular volume and mass and their relationship to standard intracardiac pressure and flow determinations are presented for each group in order to define the hemodynamic and functional characteristics of the left ventricle in these patients. Mean values for end-diastolic volumes (EDV) in the three groups were AS=85 ml/m2, AS+AR=143 ml/m2 and AR=197 ml/m2. Mean values for ejection fraction (EF=SV/EDV) were similar in the three groups, AS=61%, AR= 55%, AS+AR=58%.Left ventricular mass (LVM) was smaller in AS, mean=167 g/m2, and similar in AR, mean=232 g/m2, and AS+AR, mean=235 g/m2. Left ventricular filling pressure (LVEDP) was correlated with EDV in AS, r=0.45, P<0.05, and AS+AR, r=0.51, P<0.001, but not in AR. A similar relationship was seen between LVEDP and EF. The arteriovenous oxygen difference correlated well with EF in AS, r=−0.76. P<0.001. This relationship was weaker in AS+AR, r= −0.45, P<0.01, and AR, r=−0.45, P<0.01. Correlations were also present between increased LVM and elevated LVEDP and increased LVM and decreased EF in patients with AS and AS+AR.

Treatment of asystole or heart block during acute myocardial infarction with electrode catheter pacing

Abstract 1. 1. Clinical experience with the use of a bipolar catheter electrode pacemaker is reported in 7 patients with acute myocardial infarction complicated by Adams-Stokes attacks due to asystole or complete heart block. 2. 2. The use of a bipolar catheter electrode for 2 to 6 days resulted in spontaneous return of normal sinus rhythm in 6 patients, whereas another patient had a permanent pacemaker implanted surgically 6 weeks later. 3. 3. Mortality was reduced to 14 per cent; the one fatality occurred in the single patient who was catheterized twice, but who died unexpectedly on the thirteenth day. Survivors have returned to work after recovery from infarction. 4. 4. Problems in management, especially with unstable cardiac mechanisms and conduction during a transition period in recovery, have been cited.

The hemodynamic effects of diphenylhydantoin

Abstract This study records the first observations in human beings on the hemodynamic effects of diphenylhydantoin (DPH). Alterations were not noted in cardiac output, peripheral resistance, pulmonary pressures, or the electrocardiogram when the drug was administered in doses previously noted to be clinically effective in cardiac arrhythmias. Animal studies have shown that DPH directly reduces ventricular function and results in vasodilatation, but that the cardiovascular toxicity is probably related more to the rapidity of injection than to the absolute dose. The pharmacologic actions of DPH resemble those of quinidine and procainamide, with the exception that DPH has not been shown to be effective against chronic atrial flutter and fibrillation, and that in small doses it may greatly augment vagal tone. The conclusion is that, in this study, even though DPH did not significantly alter cardiovascular function, it possesses significant toxic potential, and should be administered cautiously and in doses not exceeding 10 mg. per kilogram.

Myocardial Infarction After Normal Responses to Maximal Exercise

The unexpected occurrence of acute myocardial infarction shortly after performance of a multistage test of maximal exercise by a normal 42-year-old subject is described. There was no evidence of infarction after this exhausting effort, but symptoms occurred immediately on exposure to hot water while he was taking a shower a few minutes later. Cardiac arrest from ventricular fibrillation occurred after ECG evidence of acute infarction. Following successful defibrillation and coronary care, there was satisfactory recovery from massive anterior wall infarction. Incidence, possible pathophysiological mechanisms, and precautions are cited.

Physiological Significance of Maximal Oxygen Intake in "Pure" Mitral Stenosis

Acute circulatory and respiratory adjustments to mild through maximal upright exercise were studied in seven patients with “pure” mitral stenosis. Maximal oxygen uptake was determined objectively by demonstrating a plateau of oxygen uptake with increasing workloads. Time to reach a plateau of oxygen uptake was normal (2 to 3 minutes) at all workloads. At any given oxygen uptake, cardiac output and hepatic clearance of indocyanine green (ICG) were abnormally low while total arteriovenous (A-V) oxygen difference, heart rate, blood lactate, and ventilation were abnormally high. However, with respect to relative oxygen uptake (per cent of maximal oxygen uptake), the reduction in cardiac output was exaggerated, but A-V oxygen difference, heart rate, blood lactate, and hepatic clearance of ICG were essentially normal. RQ and VE/VO2 were quantitatively abnormal even with respect to relative oxygen uptake, but the pattern of changes from mild to maximal exercise was normal. Low maximal oxygen uptake defined the reduction in stroke volume while other circulatory responses were normal with respect to relative oxygen uptake.