George C. Curry

Intraaortic balloon counterpulsation in patients in cardiogenic shock, medically refractory left ventricular failure and/or recurrent ventricular tachycardia

Of the 27 patients described, 23 were in cardiogenic shock, 2 had severe left ventricular failure, and 2 had medically refractory ventricular tachycardia. Utilizing intraaortic counterpulsation, adequate systemic blood pressure was initially restored in 19 patients. Nine of these were subsequently weaned from circulatory assistance, but only three were discharged from the hospital and are currently alive. The remaining 10 patients who derived initial benefit from circulatory assistance were balloon-dependent in that they could not be weaned from circulatory assistance. Eight of these patients subsequently underwent cardiac catheterization; four had inoperable disease. The remaining four patients underwent surgery for either resection of the area of infarction and/or for myocardial revascularization; only one survived to subsequently leave the hospital. Ventricular volumes were abnormal and ejection fractions were below 30 per cent in all the patients in cardiogenic shock except one who underwent cardiac catheterization and ultimately died. Ejection fractions were greater than 30 per cent in the two patients with cardiogenic shock who were weaned from balloon support and survived to leave the hospital without surgery. Both of these patients had inferior myocardial infarction. The data obtained from this experience suggest that intraaortic counterpulsation is a very useful adjunct to currently existing medical measures to treat both cardiogenic shock and medically refractory left ventricular failure but that most patients have such extensive disease that they can neither be weaned from balloon support nor undergo successful infarctectomy or myocardial revascularization.

Unstable angina pectoris. Clinical, angiographic, and myocardial scintigraphic observations.

The clinical, left ventricular and coronary angiographic data, and the technetium-99m stannous pyrophosphate (99mTc-PYP) myocardial scintigraphic results are presented in 31 patients with unstable angina pectoris. One-third of these patients had positive 99mTc-PYP myocardial scintigrams in a pattern suggesting limited and diffuse subendocardial necrosis. The positive 99mTc-PYP myocardial scintigrams occurred without diagnostic electrocardiographic and cardiac enzyme changes suggestive of myocardial infarction; positive scintigrams seemed to occur more commonly in patients with continuing pain after admission and in those without previous history of myocardial infarction. The positive 99mTc-PYP myocardial scintigrams did not correctly predict coronary anatomical patterns except that positive scintigrams occurred only in patients with coronary artery disease. Neither did the positive scintigrams necessarily occur in that group of patients with the poorest ventricular function though the 2 patients with the lowest ejection fractions both had positive 99mTc-PYP myocardial scintigrams. Finally, when positive 99mTc-PYP scintigrams are the only evidence suggestive of limited subendocardial infarction in patients with unstable angina pectoris, they do not appear to have any prognostic significance in terms of longevity or response to pharmacological or surgical therapy, though the follow-up period so far is short.

Unstable angina pectoris: a randomized study of patients treated medically and surgically.

Fifty patients with the clinical syndrome of unstable angina pectoris were evaluated. Twenty-seven were randomized into medical or surgical treatment groups and subsequently followed up. The results of the study reveal that: (1) there is approximately a 16 percent incidence rate of significant left main coronary artery disease in patients with this entity at our institution; (2) 10 percent of patients do not have angiographically significant coronary artery disease; (3) pain relief is better in the surgically treated patients, but the 1 1/2 year survival rate is not significantly different between the groups; (4) 50 percent of the medically treated patients again had the syndrome of unstable angina pectoris in the initial few months of the follow-up period; (5) the operative and late postoperative mortality rate in patients presenting with unstable angina pectoris and left main coronary artery disease in this small group of patients was 43 percent; and (6) four of six patients with this syndrome whose condition was deemed inoperable and who were not randomized died within the subsequent few months.

Influence of hypertonic mannitol on ventricular performance and coronary blood flow in patients.

The influence of a relatively small increase in serum osmolality produced by hypertonic mannitol on ventricular and systemic arterial hemodynamics and coronary blood flow was studied in 20 patients undergoing cardiac catheterization. Mannitol given to increase serum osmolality 10 mOsm resulted in a small but significant increase in mean systemic arterial pressure, maximum LV dp/dt, left ventricular end-diastolic pressure and cardiac output but no significant change in heart rate or hematocrit. The most prominent change in the patients studied, however, was in coronary blood flow which increased 39% after mannitol. Patients with severe two and three vessel coronary artery disease had increased in coronary blood flow similar to those in patients without coronary artery disease. The data suggest the need to further evaluate the physiological importance of the increase in coronary blood flow produced by mannitol in patients with coronary artery disease and indicate the possibility that mannitol might be of value in treating certain problems in patients with coronary artery disease,

Differentiation of Physiologically Significant Coronary Artery Lesions by Coronary Blood Flow Measurements During Isoproterenol Infusion

At cardiac catheterization, the effect of isoproterenol on coronary blood flow was compared in six patients with normal coronary arteries and normal left ventricular function, and eight patients with angiographically defined coronary lesions. Coronary blood flow was measured by selective coronary artery injection of xenon-133 and external monitoring of disappearance curves with a dual probe, digital scintillation counter. Resting values did not differ in the two groups. In the normal group isoproterenol increased mean coronary blood flow 93 ml/100 g/min (152%) and cardiac output 2.3 liters/min (42%); coronary resistance/100 g decreased 60 ± 4% (SEM), while total peripheral resistance decreased 29 ± 4%. In the coronary disease group coronary blood flow increased 20 ml/100 g/min (33%) and cardiac output increased 2.8 liters/min (62%); coronary resistance decreased 26 ± 9% and total peripheral resistance decreased 37 ± 4%. In all normal patients the percent increase in coronary blood flow markedly exceeded the percent increase in cardiac output and the percent fall in coronary resistance markedly exceeded the percent fall in total peripheral resistance. In six of the eight patients with coronary lesions the percent increase in coronary blood flow was less than the percent increase in cardiac output and the fall in coronary resistance was less than the fall in total peripheral resistance. Thus measurement of coronary blood flow, cardiac output, and aortic pressure before and during isoproterenol infusion may permit differentiation of those subjects with physiologically significant coronary obstructions.

The influence of hypertonic mannitol on regional myocardial blood flow during acute and chronic myocardial ischemia in anesthetized and awake intact dogs.

The influence of hypertonic mannitol on regional myocardial blood flow and ventricular performance was studied during acute myocardial ischemia in awake, unsedated and in anesthesized dogs and after myocardial infarction in awake unsedated dogs. Regional myocardial blood flow was measured with radioactive microspheres. Generalized increases in regional myocardial blood flow occurred after mannitol in all of the different animal models studied. The increases in coronary blood flow after mannitol were just as impressive in the nonischemic regions as in the ischemic portion of the left ventricle in all of the different models that were examined in this study. Improvement in regional myocardial blood flow to the ischemic area of the left ventricle after mannitol was associated with a reduction in ST segment elevation during acute myocardial ischemia in anesthetized dogs. The increases in regional myocardial flow after mannitol were also associated with increases in contractility, but the increases in flow appeared to be more impressive than the changes in contractility. The data obtained demonstrate that mannitol increases regional coronary blood flow to both ischemic and nonischemic myocardium in both anesthetized and awake, unsedated, intact dogs with acute and chronic myocardial ischemia and that mannitol reduces ST segment elevation during acute myocardial ischemia in anesthetized dogs. Thus the results suggest that under these circumstances the increases in regional myocardial blood flow after mannitol are of physiological importance in reducing the extent of myocardial injury. Since coronary blood flow increased to nonischemic regions the increases in regional myocardial flow demonstrated in this study after mannitol cannot be entirely explained by the mechanism of reduction in ischemic cell swelling.

Effect of Isoproterenol on Coronary Blood Flow in Primary Myocardial Disease

At cardiac catheterization, the effect of isoproterenol on coronary blood flow was compared in six patients with primary myocardial disease and six patients who appeared to have no cardiac disease. Coronary blood flow was measured by selective coronary artery injection of xenon-133 and external monitoring of disappearance curves with a dual probe, digital scintillation counter. In the presence of similar changes in cardiac output and heart rate-systolic pressure product, changes in coronary blood flow and coronary resistance in response to isoproterenol were significantly less (P < 0.05) in the subjects with primary myocardial disease than in the normal subjects.

Radionuclide Determination of Myocardial Blood Flow

The diffusible-indicator method of determining tissue blood flow was devised by Kety and his associates, 1–3 who observed the washout of an intraarterially injected tracer from the tissue of interest, and found that it was proportional to tissue blood flow. Ketys original tracer was nitrous oxide, but he soon adapted his method to the use of 24 Na. Other investigators developed Ketys method further, substituting 85 Kr, and ultimately, 133 Xe as diffusible indicators. It has been found that if 133 Xe is injected directly into a coronary artery and its washout from myocardium is observed with a scintillation probe over the precordium, the resulting determination, mean myocardial blood flow, is of limited application. Since coronary artery disease is a regional process, the most useful determination is one that yields regional myocardial blood flow. This may be determined by one of the original Kety methods, 3 i.e., observing the washout of tracer injected directly into the myocardium, but since it requires thoracotomy this method is not widely applicable. Several groups have assembled instrument systems based on the use of scintillation camera-computer combinations with which they can enter the image of the passage of a bolus of intracornoary arterially injected tracer, and by means of image data quantification derive regional myocardial blood flow values by Ketys method. The authors have studied more than 130 dogs before and after experimental coronary embolization and have described a complete method of deriving regional myocardial blood flows with an Anger camera-small computer system. Analysis of flow curves thus generated has suggested the existence of more than one compartment within myocardial blood flow. These compartments might be related to primary/collateral flow or to the volume of perfused tissue incorporated in the region of interest. Cannon et al. 25–27 have employed a multicrystal camera of the autofluoroscope type and an IBM 360/91 computer, in which the camera functions as 294 isolated detectors for the purpose of identifying as many regions of myocardial blood flow. Cannon et al. have studied both normal human subjects and patients with radiographically demonstrable coronary artery disease and have found regional flow to be a valid method both for identifying the myocardial flow inhomogeneities expected with coronary artery disease and for evaluating the results of reparative surgery.