The rate-pressure product as an index of myocardial oxygen consumption during exercise in patients with angina pectoris

In order to evaluate hemodynamic predictors of myocardial oxygen consumption (MVO2), 27 normotensive men with angina pectoris were studied at rest and during a steady state at sympton-tolerated maximal exercise (STME). Myocardial blood flow (MBF) was measured by the nitrous oxide method using gas chromatography. MBF increased by 71% from a resting value of 57.4 +/- 10.2 to 98.3 +/- 15.6 ml/100 g LV/min (P less than 0.001) during STME while MVO2 increased by 81% from a resting value of 6.7 +/- 1.3 to 12.1 +/- 2.8 ml O2/100 g LV/min (P less than 0.001). MVO2 correlated well with heart rate (HR) (r = 0.79), with HR x blood pressure (BP) (r = 0.83), and, adding end-diastolic pressure and peak LV dp/dt as independent variables, slightly improved this correlation (r = .86). Including the ejection period (tension-time index) did not improve the correlation (r = 0.80). Thus, HR and HR x BP, both easily measured hemodynamic variables, are good predictors of MVO2 during exercise in normotensive patients with ischemic heart disease. Including variables reflecting the contractile state of the heart and ventricular volume may further improve the predictability.

Aortic regurgitation associated with ventricular septal defect. Echocardiographic and hemodynamic observations

Ventricular septal defect is sometimes associated with aortic regurgitation. In this report, an echocardiogram demonstrating dramatic prolapse of the noncoronary cusp into the left ventricular outflow tract and ventricular septal defect in a patient with Down's syndrome and ventricular septal defect, confirmed by angiographic studies, is presented. The echocardiogram supports the concept of anatomic lack of support of the aortic ring due to a deficient septum and hemodynamically significant flow of blood to the right ventricle through the ventricular septal defect, resulting in trauma to aortic cusps and prolapse.

Methotrexate in blood, urine, and cerebrospinal fluid of children receiving high doses by infusion

Methotrexate was determined in plasma (31 patients), urine (eight patients), and cerebrospinal fluid (two patients) after high doses (35 to 150 mg/kg) by infusion, with citrovorum factor rescue. Concentrations in plasma were proportional to dose at 6, 24, 72 h after beginning treatment, but this trend was very minimal for samples obtained at 48 h. Clinical toxicity probably will not be serious if the methotrexate concentration in the serum is less than 4.5 X 10(-6) mol/liter at 48 h after the start of a 6-h infusion. In both of the two patients so examined, therapeutic concentrations appeared in cerebrospinal fluid after intravenous infusion of the drug. A kinetic enzymic method, radioassay, and radioimmunoassay all yielded similar results for drug concentrations.

Methotrexate in blood, urine, and cerebrospinal fluid of children receiving high doses by infusion

Methotrexate was determined in plasma (31 patients), urine (eight patients), and cerebrospinal fluid (two patients) after high doses (35 to 150 mg/kg) by infusion, with citrovorum factor rescue. Concentrations in plasma were proportional to dose at 6, 24, 72 h after beginning treatment, but this trend was very minimal for samples obtained at 48 h. Clinical toxicity probably will not be serious if the methotrexate concentration in the serum is less than 4.5 X 10(-6) mol/liter at 48 h after the start of a 6-h infusion. In both of the two patients so examined, therapeutic concentrations appeared in cerebrospinal fluid after intravenous infusion of the drug. A kinetic enzymic method, radioassay, and radioimmunoassay all yielded similar results for drug concentrations.

Demonstration of acid mucopolysaccharides in the trabecular meshwork of the Rhesus monkey

The ability to demonstrate AMPS in the trabecular region in the normal eye of the Rhesus monkey was shown to be critically dependent upon technical variation. Staining the fixed specimen prior to dehydration and embedding permits the uniform demonstration of AMPS in the trabecular region of the Rhesus monkey and shows it to be hyaluronidase-sensitive. Electron microscopy using the modified technique shows the reaction products to be present within the trabecular band, the intertrabecular spaces, and the canal of Schlemm. More impressive distribution was seen in the basement membrane of trabecular endothelium intimately related to the cell wall and in the ground substance and basement membrane of the endothelium of the inner wall of the canal Schlemm. The technique is also successful in the human eye and suggests a greater abundance of trabecular AMPS in open-angle glaucoma.

Hemodynamic changes during ventricular pacing in patients with complete heart block and aortic and mitral valvular heart disease

Increasing the heart rate to near normal in patients with complete heart block (CHB) and slow ventricular rates may lead to greater improvement in ventricular function than when the heart rate is increased from normal to more rapid heart rates. Improvement in ventricular function is usually manifested by a decrease in left ventricular end-diastolic pressure (LVEDP) and volume and by an increase in contractility. In patients with both CHB and valvular heart disease improvement in ventricular function during pacing may be modified by the nature of the valvular disease. Hemodynamic data from six patients with both valvular heart disease and CHB were compared with those from ten patients with CHB and normal cardiac valves. Hemodynamic studies were performed at slow or idioventricular rates and again after increasing the heart rate to more nearly normal levels by ventricular pacing. When obstruction to left ventricular inflow (mitral stenosis) co-existed with CHB, increasing the heart rate resulted in a reduction of an elevated LVEDP to normal. This resulted in only a small increase in left atrial pressure in spite of a striking increase in the mean left atrial-ventricular gradient. When obstruction to left ventricular outflow prevailed (aortic stenosis), improvement in cardiac function was manifested mainly by a decrease in LVEDP and was accompanied by a decrease in left ventricular stroke work. When a large regurgitant volume (aortic insufficiency) was added to a ventricle which has enlarged subsequent to CHB, there was striking elevation in ventricular filling pressures which returned to more nearly normal levels when the heart rate was increased. This was accompanied by a reduction in regurgitant stroke volume in the patient in whom it was measured. Thus, an increase in heart rate may be especially beneficial to those patients with CHB who also have valvular lesions which contribute to an increase in LVEDP and end-diastolic volume. Careful hemodynamic evaluation is helpful in determining appropriate therapy in these patients.

Hemodynamic predictors of myocardial oxygen consumption during static and dynamic exercise

Hemodynamic predictors of myocardial oxygen consumption (MVO 2 ) during static and dynamic exercise were examined in ten normal subjects. Studies were done under the following circumstances: 1) during upright bicycle exercise at an average heart rate of 147 beats/min, 2) during static exercise with an isometric load in the left hand equal to 17% of the maximal voluntary contraction (MVC), and 3) during combined dynamic exercise (average heart rate 147 beats/min) and static exercise using 17% MVC of the left hand. Mean myocardial blood flow (MBF) was 181 ml/100 gm LV/min during dynamic exercise, 98 ml/100 gm LV/min during static exercise, and 201 ml/100 gm LV/min during combined static and dynamic exercise. Addition of a static load to the dynamic load resulted in a higher blood pressure (average 12 mm Hg), MVO 2 and MBF than during dynamic exercise alone. MVO 2 correlated best with products of heart rate and blood pressure regardless of whether the blood pressure was obtained by a central aortic catheter ( r = 0.88) or by a blood pressure cuff ( r = 0.85).

When the current data were combined with previous data, 82 determinations of MVO 2 and MBF in 29 normal subjects during several levels of upright exercise were available for analysis. Forty-four determinations were done during dynamic upright exercise, 18 during exercise after propranolol, ten during combined static and dynamic work, and ten during static work alone. MVO 2 correlated best with the product of heart rate and blood pressure ( r = 0.86). Heart rate alone correlated better with MVO 2 ( r = 0.82) than did the tension time index ( r = 0.65) or the product of systolic blood pressure, heart rate, and ejection time ( r = 0.68). The readily measured variables of heart rate and of heart rate x blood pressure correlated well with MVO 2 in normal young men during exercise under a wide variety of circumstances.

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.

Serum lactate dehydrogenase elevation in ambulatory cardiac patients. Evidence for chronic hemolysis

Activity of total lactate dehydrogenase (LDH) and that of the heat-stable isozyme (LDH-1) was measured by the method of Strandjord and Clayson in the serum of 62 cardiac patients with congenital and valvular heart disease before and after cardiac catheterization and at follow-up examination after cardiac surgery. A universal elevation of both total and heat-stable LDH was found in patients with prosthetic heart valves of several types. Lesser degrees of abnormalities were seen in a number of the patients without prosthetic devices. Some patients had a small increase in serum enzyme activity the day after cardiac catheterization. The evidence presented implicates hemolysis in the production of these abnormalities. It is suggested that all patients with prosthetic valves and a significant percentage of patients with severe hemodynamic abnormalities have chronic, usually compensated, intravascular hemolysis secondary to mechanical damage to red blood cells. These findings must be kept in mind in interpreting serum LDH determinations in patients with valvular prostheses or congenital and valvular heart disease who present with complaints of chest pain.