Effect of propranolol on myocardial oxygen consumption and its hemodynamic correlates during upright exercise

Measurements were made of heart rate, aortic blood pressure, systolic ejection period/beat, myocardial blood flow, and myocardial oxygen consumption in nine normal young men during three bouts of upright bicycle exercise: 1) at the workload which produced a heart rate of 120 beats/minute, 2) at the higher workload necessary to produce a heart rate of 120 beats/minute after administration of intravenous propranolol 0.25 mg/kg, and 3) with infusion of propranolol, at the same workload as the first exercise bout. Comparing exercises 1 and 2, we found a much higher workload was required to produce the same heart rate after propranolol. The blood pressure, heart rate-blood pressure product, and myocardial oxygen consumption were the same despite the much greater level of exertion. Comparing exercises 1 and 3, the heart rate, blood pressure, heart rate-blood pressure product, and myocardial oxygen consumption were all significantly lower during exercise 3 after propranolol despite the fact that the same degree of exercise was being done. As in previous studies, the heart rate-blood pressure product was an excellent correlate of myocardial oxygen consumption despite the change in contractility induced by propranolol. The systolic ejection period was prolonged significantly altering the tension-time index (TTI), which became an inadequate index of myocardial oxygen consumption. It is concluded that the heart rate-blood pressure product is a good index of myocardial metabolic needs during exercise and the relationship is undistorted by marked changes in contractility, but the tension-time index is a poor correlate. This data emphasizes the fact that the relative metabolic loads for the whole body and for the heart are determined separately and may not change in parallel with a given intervention.

Left ventricular ejection time in valvular aortic stenosis

Hemodynamic data obtained at cardiac catheterization from 40 patients with valvular aortic stenosis demonstrated that, although left ventricular ejection time was prolonged, the usual linear inverse relationship between heart rate and ejection time was preserved at a longer than normal mean ejection time. In contrast to this, the direct linear relationship between ejection time and stroke volume which exists in normal human subjects was totally obliterated in patients with aortic stenosis so that ejection time appeared to be totally unrelated to stroke volume. However, the degree of prolongation of left ventricular ejection time above that predicted from stroke volume (ΔLVET) was closely correlated with aortic valve area (AVA), so that aortic valve area could be predicted as AVA = 0.91 – 3.6 ΔLVET within 95% confidence limits of ± 0.16 cm 2 . Alternatively, if ejection time was not abnormally prolonged, it was possible to predict with 95% confidence that the aortic valve area was greater than 0.75 cm 2 in cross-sectional area and thus not within the range generally requiring surgical therapy.

Hemodynamic effects of exercise in isolated valvular aortic stenosis

Hemodynamic data, including simultaneously measured left ventricular and aortic pressures, were obtained from 20 patients with isolated valvular aortic stenosis at rest and during supine leg exercise. Changes in left ventricular end-diastolic pressure during exercise were not significantly related to the severity of aortic stenosis but were correlated with age; patients with abnormal left ventricular end-diastolic pressures during exercise were significantly older than those in whom this variable remained normal. Exercise resulted in significant increases in both the mean rate of systolic aortic blood flow and the mean systolic pressure gradient across the aortic valve. Analysis of this pressure gradient demonstrated symmetrical shortening of the ejection time per beat with an increase of the maximal systolic pressure gradient during exercise. Although changes in mean systolic aortic pressure gradient and mean aortic flow were significantly positively correlated, the increases in mean systolic pressure gradient during exercise were less than predicted from corresponding increases in mean aortic flow; thus the result was an apparent increase in computed aortic valve area.

Acute changes in left ventricular volume and contractility during ventricular pacing in patients with complete heart block

To determine whether changes in preload and contractility may account for clinical improvement in patients with complete heart block (CHB) when the ventricular rate is increased by pacing, 10 hemodynamic studies were performed in nine patients with CHB. Left ventricular end-diastolic volume (EDV) was measured before and during pacing by the dye-dilution and the angiographic techniques. Changes in contractility were assessed from the first derivative of ventricular pressure divided by a common peak isovolumic pressure (CPIP) to correct for afterload and by EDV to correct for preload. EDV decreased during pacing, the mean value decreasing from 242 to 180 ml ( P < 0.001). Since the left ventricular dp/dt is influenced by afterload and preload, improvement in contractility indices was consistent only after allowances were made for changes in aortic diastolic pressure and EDV. The mean dp/dt/CPIP divided by EDV increased from 0.120 to 0.160 ( P < 0.005). The mean left ventricular enddiastolic pressure decreased from 17.0 to 9.7 mm Hg ( P < 0.05) during pacing, while the mean cardiac index increased from 2.0 to 2.5 liters/min/m 2 ( P < 0.025). The clinical improvement seen after pacing in patients with CHB results, in part, from an increase in contractility and a decrease in EDV and pressure.

The freon test. A new sensitive technic for the detection of small cardiac shunts

A new, sensitive, qualitative technic is described for detecting small left-to-right and right-to-left circulatory shunts. Advantages over other sensitive shunt detection devices are: (1) the use of a readily available, nonradioactive, nonexplosive, nontoxic gas, namely Freon 22; (2) the ability to sample through standard cardiac catheters as small as 5F; (3) an immediate answer due to recording of the gas concentration in blood; and (4) extremely high sensitivity allowing the detection of the smallest left-to-right and right-to-left shunts.

The hemodynamic results of instrumental and digital valvotomy in patients with mitral stenosis

In order to evaluate the postoperative results from mitral valvotomy when patients were selected according to age, sex, cardiac rhythm, and mode of operation, the mitral valve area (MVA) was determined by cardiac catheterization in 32 patients before and 1 year following closed mitral valvotomy. There was a significantly greater increase in MVA in female patients, younger patients, and patients with sinus rhythm than in males, patients over 45 years of age, and patients with atrial fibrillation. Patients who had an instrumental valvotomy (20 patients) did not have a greater postoperative increase in MVA than patients who had a digital valvotomy (12 patients); however, patients with the largest postoperative MVA had instrumental valvotomy. The incidence of postoperative mitral insufficiency was similar in patients with digital and instrumental valvotomy. Small flecks of mitral valve calcification, as determined by preoperative image-intensification fluoroscopy, did not influence the postoperative MVA.

Immediate hemodynamic response of patients with atrioventricular block and cardiac failure to transvenous pacing

Immediate hemodynamic improvement in patients with complete heart block occurs when the ventricular rate is increased by electrical pacing. During pacing, there is reduction in the pulmonary artery wedge, right atrial, and left and right ventricular filling pressures. The mean rate of ejection, stroke volume, and stroke work decreased following pacing, whereas the ejection time per minute increased, and dye curves assumed a more normal configuration. Very little change was noted in the resting cardiac output.

The paced heart is able to obtain greater increases in cardiac output, stroke volume, and mean rate of ejection during exercise than when unpaced. In addition, pacing tends to return elevated exercising filling pressures in the right and left ventricles toward normal.

Acute myocardial infarction secondary to thromboembolism from a fractured prosthetic aortic valve

A case of coronary artery embolism from thrombus in a fracture in an aortic Starr-Edwards prosthesis was documented at necropsy. This 40-year-old white man had replacement of the aortic and mitral valves by ball-valve prostheses 5 years prior to his death. Following surgery, he was able to return to full-time work. He did not return for follow-up for 2 years, and when next seen he had an acute myocardial infarction and left ventricular failure. An embolus to the left anterior descending coronary artery was demonstrated at the postmortem examination. The mitral ball was intact, but the aortic ball had two large fractures which contained thrombi.