Mechanisms of angina in aortic stenosis

Myocardial oxygen supply in left ventricular hypertrophy and coronary heart disease

Coronary arteriolar dilation adjusts blood flow according to local fluctuating metabolic needs of the myocardium. Because of high extravascular compression during systole, the subendocardial layer of the left ventricle is especially dependent on the duration and the perfusion pressure of the diastolic period. In patients with obstructive coronary artery disease, regional arteriolar dilation is utilized to compensate for focal arterial stenoses. Coronary blood flow may be compensated with the patient at rest, but loss of reserve arteriolar dilation limits further adjustment to superimposed transient increases in metabolic needs. Subendocardial perfusion in the region supplied by the stenosed artery is especially vulnerable to shortened diastolic time during tachycardia. In patients with chronic aortic valve disease, the metabolic rate of the left ventricle is increased in proportion to the increases in myocardial mass and work. Coronary blood flow and metabolic rate per gram of the hypertrophied myocardium are normal when the patient is at rest, at the expense of diminished coronary arteriolar reserve. High tissue pressure relative to the diastolic perfusion pressure probably contributes to the diffuse subendocardial ischemia that occurs in these patients during tachycardia.

Influence of preoperative left ventricular function on results of homograft replacement of the aortic valve for aortic stenosis

The effect of preoperative left ventricular function on early and late prognosis was assessed in 103 patients with aortic stenosis who underwent left ventricular cineangiography before homograft replacement of the aortic valve. The patients were separated into two groups: Group A (58 patients) with an ejection fraction of 0.46 or more and Group B (45 patients) with an ejection fraction of 0.45 or less. The two groups were compared with respect to clinical and hemodynamic data as well as operative result. There was poor correlation between clinical data and left ventricular function. In Group A there were three early deaths (5.2 percent) and three late deaths (5.2 percent) compared with no early and six late deaths (13.3 percent) in Group B during the follow-up period of 12 to 102 months (mean 43 months). Most patients in Group B showed considerable symptomatic improvement but less than that observed in Group A. Forty-two patients (13 in Group A and 29 in Group B) underwent repeat cardiac catheterization and coronary angiography. Improvement in left ventricular function as assessed by radial analysis of segmental wall motion and ejection fraction was observed in 20 of the 29 patients in Group B. Failure of left ventricular function to improve was associated with additional coronary artery disease in the majority of patients. It is concluded that poor left ventricular function does not increase the risk of aortic valve replacement for aortic stenosis and that improvement in left ventricular function can be expected in the majority of patients.

Angina, aortic stenosis and coronary heart disease

The pre-operative clinical and haemodynamic findings of 139 consecutive patients with aortic stenosis were analysed in an attempt to determine the incidence and influence of coronary heart disease on the mode of presentation of patients with aortic stenosis. The overall incidence of coronary heart disease was 32%. 105 patients (76%) presented with angina and of these, 41 patients (39%) had significant coronary heart disease as compared to 4 (13%) of the remaining 34 patients who did not present with angina. Clinical parameters including age, sex, severity of angina together with the presence of associated symptoms and precipitating factors were unhelpful in distinguishing those patients with coronary heart disease. Evidence of previous transmural myocardial infarction or the presence of ST-T abnormalities in the absence of digitalis and the changes of left ventricular hypertrophy were reliable electrocardiographic signs of coronary heart disease. Although peak systolic aortic valve gradient tended to decrease with increasing severity of coronary heart disease, the severity of aortic stenosis was not a reliable indicator of the presence of coronary disease. Patients with coronary heart disease in the absence of angina all had a combination of moderate aortic stenosis and single vessel disease. It is concluded that coronary heart disease cannot be predicted in patients with angina and, in the absence of angina occurs with an incidence sufficiently high to advocate the use of coronary angiography as part of the investigation of all patients with aortic stenosis being considered for valve replacement.

Pre-infarction angina secondary to calcific aortic stenosis with Bernheim's effect

Pre-infarction angina, in the absence of coronary artery disease, was found in a 62 year-old man with severe calcific aortic stenosis. After application of intraaortic balloon pump counter-pulsation, the condition was stabilized, and coronary arteriograms were safely carried out. Interestingly, an elevated right atrial and right ventricular end-diastolic pressure with an associated Bernheim's effect was demonstrated by cardiac catheterization. The hemodynamics of the right heart returned to normal after surgical correction of the aortic stenosis. The clinical indications for intra-aortic balloon pump counterpulsation in this setting are discussed.

Medical therapy of angina pectoris

The pathophysiology of angina pectoris is best understood as an imbalance between oxygen supply and demand. The primary determinants of myocardial oxygen demand are heart rate, arterial pressure, heart size, myocardial contractility, and myocardial mass. The medical therapy of angina pectoris is directed toward reducing myocardial oxygen demand by reducing the workload of the heart and the specific determinants listed. The most common medications used in the treatment of angina pectoris are nitroglycerin and propranolol. Nitroglycerin reduces myocardial oxygen demand primarily by reducing heart size and arterial pressure. Propranolol reduces oxygen demand primarily by reducing heart rate. Medical therapy is generally effective in controlling the symptoms of angina pectoris in 80% or more of the patients and allows them to lead useful and productive lives.

The prevalence of angina pectoris and abnormal coronary arteriograms in severe aortic valvular disease

In order to relate the frequency of angina pectoris to associated coronary artery disease, 66 consecutive patients with severe aortic valvular disease were studied by cardiac catheterization, including coronary angiography. Angina pectoris was found in 63 per cent of patients with predominant aortic stenosis, 62 per cent with aortic regurgitation, and 67 per cent with mixed disease. Associated coronary artery disease (larger than or equal to 75 per cent luminal stenosis) ranged from 14 to 28 per cent and averaged 20 per cent for the entire group of 66 patients. Only one patient without angina had significant coronary artery stenosis. Our studies indicate that angina pectoris is equally common in all forms of severe aortic valve disease and is usually not associated with significant coronary artery disease.

Chest pain as a predictor of coronary artery disease in patients with obstructive aortic valve disease

To clarify the association between chest pain and significant coronary artery disease in patients who have aortic valve disease, 76 consecutive candidates for aortic valve replacement were evaluated prospectively with use of a historical questionnaire and coronary arteriography. Of the 76 patients, 19 (25 percent) had no chest pain, 21 (28 percent) had chest pain that was not typical of angina pectoris and 36 (47 percent) had chest pain typical of anigina pectoris. In 18 of 19 patients the absence of chest pain correlated with the absence of coronary artery disease. The single patient without chest pain who had coronary artery disease had evidence of an inferior myocardial infarction in the electrocardiogram. Thus, absence of chest pain and the absence of electrocardiographic evidence of infarction predicted the absence of coronary disease in all cases. The presence of chest pain did not predict the presence of coronary artery disease, but the more typical the pain of angina pectoris the more likely were patients to have significant coronary artery disease. Of the 21 patients with atypical chest pain, 6 (29 percent) had coronary artery disease, but of the 36 patients with typical angina pectoris 23 (64 percent) had significant coronary artery disease. In addition, when patients with chest pain not typical of angina pectoris also had coronary artery disease, the diseased vessels usually supplied smaller areas of the left ventricle than when the pain was typical of angina pectoris. In 21 of 23 patients (91 percent) with typical angina pectoris and significant coronary artery disease, lesions were present in the left coronary artery. There was no systolic pressure gradient across the aortic valve that excluded the presence of coronary artery disease, although all patients with a calculated aortic valve area of less than 0.4 cm2 were free of coronary artery disease. Patients with severe left ventricular dysfunction were more likely to have normal coronary arteries.

Corrected transposition of the great arteries simulating coronary heart disease in adults

Two middle-aged adults with corrected transposition of the great arteries presented with chest pain and dyspnea, initially attributed to coronary arterial disease with left ventricular dysfunction and mitral regurgitation. The clinical diagnosis of coronary arterial disease was supported in these patients by electrocardiographic changes of probable old anteroseptal myocardial infarction and by an abnormal cardiac silhouette on the chest x-ray film suggestive of ventricular aneurysm. Coronary arteriographic studies in both patients showed that the morphologic left coronary artery supplied the venous ventricle, and the right coronary artery supplied the systemic ventricle. Neither patient had coronary arterial luminal narrowing. We propose that anginal chest pain in these patients resulted from inadequate coronary reserve of the morphologic right ventricle functioning as a systemic ventricle.

Aortic stenosis, angina pectoris, coronary artery disease

The data from 88 patients (pts) with aortic stenosis (AS) were reviewed to determine relationships between angina pectoris (AP) and coronary artery disease (CAD). Results of surgery performed in 81 of these pts was analyzed. All pts had coronary arteriograms, and lesions greater than or equal to 50% were considered significant. Fifty-nine pts had an aortic valve gradient measured at catheterization greater than or equal to 40 mmHg, and in 29 pts, AS was confirmed at operation. Sixty-eight pts (77%) experienced AP, and 32 had coexisting CAD (47%); 9 of 20 pts without AP had CAD (45%). There were no significant differences in the incidence of AP in pts divided into subgroups by the aortic valve gradient (40-50, 51-100, 101-200 mmHg) or age (40-59, 60-81 years). Also, no significant differences were found in the incidence or extent of CAD between the two age groups; the extent of CAD was similar regardless of the presence or absence of AP. In pts with AP (1) CAD was more likely in pts greater than or equal to 60 years of age; (2) CAD was less likely when the aortic valve gradient was greater than 100 mmHg, suggesting that AP in these pts was due to hemodynamically severe AS. All pts with 3-vessel CAD experienced AP, and the aortic valve gradient was less in these pts than in those with no CAD or less extensive CAD. In 19 pts with combined AS and CAD who had both the aortic valve replaced and a revascularization operation only 1 of pts died in the hospital, while 3 of 19 pts with combined AS and CAD who had aortic valve replacement alone died. In this study a significant number of pts with AS experienced AP, and the presence or absence of AP did not predict coexisting CAD. Coronary arteriography is recommended in the evaluation of pts greater than or equal to 40 years of age with AS. The operative mortality appears to be decreased in pts with AS and CAD who have combined surgery.

[Value and limitations of coronary blood flow measurement in man (author's transl)]

Attempts to measure coronary blood flow in man have made considerable progress during the last 25 years. The major techniques are based on the direct or indirect Fick principle; coronary flow is calculated from the arterio-coronary venous difference of inert gases or from the precordial recorded disappearance curve of radioactive gases or substances. The accuracy of the techniques depends upon the properties or the indicators used and the precision of their determination. All techniques applied hitherto are intricate and unsuitable for general use. -A lot of information is obtained about coronary circulation in health and disease by coronary flow measurements in man. Further studies in this field may influence pathophysiological and clinical concepts especially concerning coronary heart disease.

Effects of tachycardia on the adequacy of subendocardial oxygen delivery in experimental aortic stenosis

We studied the interaction of tachycardia and aortic stenosis on the adequacy of subendocardial oxygen delivery. In 18 open-chest dogs with acute supravalvular aortic stenosis, we produced subendocardial ischemia by increasing either heart rate (artrial pacing) or the severity of aortic stenosis. Ischemia was determined from ST-elevation of the intracavitary electrocardiogram. Subendocardial oxygen supply was assessed by measuring subendocardial flow (radioactive microspheres, 8 to 10 microns) and arterial oxygen content, and related to simultaneous oxygen demand [estimated from the tension time index (TTI)]. The adequacy of the supply/demand relationship in the subendocardium was estimated from the ratio DPTI times 02 content (supply)/TTI (demand). Subendocardial ischemia occurred at aortic gradients ranging from 30 to 100 mm. Hg and heart rates from 120 to 180 beats per minute. Ischemic hearts were characterized by (1) redistribution of coronary flow away from the subendocardium (endo/epi flow ratio less than 1.0), (2) reduced subendocardial oxygen delivery per unit of demand (TTI) (p less than 0.01), (3) failure to lower left ventricular end-diastolic pressure with tachycardia, and (4) supply/demand ratios (DPTI times 02 content/TTI) below 15 ( less than 0.01). These findings suggest that (1) the principal determinant of subendocardial ischemia in aortic stenosis is the unfavorable alteration of the supply/demand relationship caused by the interaction between heart rate and severity of stenosis, rather than absolute heart rate or aortic gradient and (2) the adequacy of subendocardial oxygen delivery can be assessed from readily obtained measurements of blood pressure and oxygen content.

Aortic stenosis, angina, and coronary artery disease. Interrelations

Sixty-nine patients over age 35 with severe valvular aortic stenosis were investigated for concomitant coronary artery disease. Forty (57.9%) had clinical angina pectoris. Sixteen (23.2%) had significant coronary occlusive disease by arteriography. Of those with angina, 13 patients (32.5) had significant coronary arterial obstruction, while in the pain-free group only (10.3%) had occlusive coronary disease. It is concluded that patients with severe aortic stenosis who are free of angina have only a small, but definite, chance of having significant coronary disease.

Ischemia in aortic stenosis: hemodynamic prediction

The records of 12 patients with aortic stenosis previously studied by Fallen et al. in 1967 before and after infusion of isoproterenol were reviewed to assess the value of hemodynamic indexes in predicting myocardial ischemia--defined as less than 5 percent transmyocardial lactate extraction or lactate production. Potential subendocardial blood supply was estimated from a diastolic pressure-time index (DPTI), calculated from the tension-time index (TTI). The ratio DPTI/TTI was used to estimate the supply/demand relation. Of eight patients with aortic stenosis but without associated coronary artery disease, four (Group A) metabolized lactate normally after administration of isoproterenol, and four (Group B) had biochemical evidence of ischemia. Three of four patients (Group C) with aortic stenosis and associated coronary artery disease had abnormal glycolysis after administration of isoproterenol. Calculated aortic valve areas were comparable in all groups. In patients with aortic stenosis alone, abnormal lactate metabolism occurred whenever DPTI/TTI was less than 0.30 (P smaller than 0.01) (Group B). Two of three patients with aortic stenosis and associated coronary artery disease (Group C) showed abnormal lactate metabolism when DPTI/TTI was greater than 0.6; this ratio was below 0.3 in the third patient. These results suggest that the supply/demand relation calculated from these readily obtained indexes may be useful (1) in predicting in which patients with aortic stenosis ischemia will develop, (2) in distinguishing the role played by associated coronary artery disease, and (3) as an adjunct to calculation of valve area since the quantitation of associated aortic regurgitation is not necessary.

Pathophysiology of subendocardial ischaemia

Most forms of heart disease cause myocardial damage which often is confined to the deep (subendocardial) layer of left ventricular muscle. Much clinical and experimental evidence suggests that subendocardial muscle is prone to ischaemic damage, and a physiological mechanism for this vulnerability is described. Furthermore, experiments suggest that pressures recorded at cardiac catheterization can help to assess if there is subendocardial ischaemia in a variety of lesions in man.