Endomyocardial biopsy diagnosis of small vessel disease: a clinicopathologic study

Hypertension and the development of heart failure

Hypertension is a well-known risk factor that predisposes to the development of left ventricular hypertrophy, coronary flow abnormalities, and systolic and diastolic dysfunction. This complex of abnormalities is known as hypertensive heart disease and eventually leads to heart failure. Structural lesions underlying this process include excess deposition of collagens and cellular infiltration, with an increase in the size of cardiac myocytes (remodeling). The occurrence of arteriolar lesions may lead to impediments of flow. Clinically, hypertensive heart disease manifests itself by anginal complaints and sometimes by silent ischemia, arrhythmias, and sudden death. Alterations in systolic and/or diastolic function may be associated with symptoms of heart failure. Although successful treatment of hypertension can probably retard the process of cardiac impairment, there is as yet no evidence that heart failure can be prevented.

Assessing the coronary circulation in hypertension

Systemic arterial hypertension is one of the major risk factors for coronary artery disease, coronary microangiopathy, and left ventricular hypertrophy, all of which can potentially lead to cardiac failure and sudden cardiac death. Coronary flow reserve is defined as the maximal increase in coronary flow above its resting, autoregulated level for a given perfusion pressure. In arterial hypertension functional and structural alterations are observed at the level of epicardial vessels as well as in resistive vessels requiring sophisticated approaches to assess coronary flow reserve and thus myocardial perfusion. Electrocardiographic tests and echocardiography can be regarded as monitoring and screening methods. Myocardial scintography is useful to semiquantitatively estimate hypertension-associated perfusion abnormalities, whereas positron emission tomography provides the only quantitative approach of a non-invasive technique for myocardial blood flow measurement. Invasive methods for the assessment of coronary blood flow need cardiac catheterization procedures, such as techniques requiring catheterization of the coronary sinus, angiographic methods, and guidewire based methods. Thermodilution and venous oxymetry in the coronary sinus systematically underestimate coronary flow reserve and are thus considered as only semiquantitative approaches. In contrast, the gas chromatographic argon method allows a quantitative measurement of coronary blood flow at baseline and during maximum vasodilation; thus it is possible to distinguish between an altered autoregulated and maximal flow as the major cause of a reduced coronary flow reserve and to evaluate long-term therapeutic interventions in hypertensive hearts. Videodensitometric and angiographic methods should be restricted only to patients with coronary microangiopathy or with coronary single-vessel disease. Guidewire-based Doppler techniques are suitable to semiquantitatively assess coronary flow reserve with a considerable spatial and time resolution. Myocardial biopsies may gain insight into hypertension-associated structural alterations in small arterioles. Long-term treatment of hypertensive heart disease aims to normalize blood pressure, to reduce left ventricular hypertrophy and to achieve cardioreparation including reversal of the abnormal structure and function of coronary circulation. Based on the different methods for assessment of coronary circulation the therapeutic value of different classes of antihypertensive therapeutics will be evaluated in this overview.

Systemic hypertension and coronary artery disease: the link

A direct, continuous, and independent association between blood pressure values and incidence of coronary artery disease has been well documented. However, the evidence that the reduction of blood pressure alone is not able to completely reverse the increase in the risk of coronary artery disease associated with essential hypertension suggests that the link between hypertension and coronary artery disease is a complex process including other factors beside the increase in blood pressure values. In this regard, the main determinant of coronary artery disease in hypertensive patients seems to be the development of left ventricular hypertrophy (LVH). In fact, hypertensive patients who died from sudden cardiac death showed a lesser degree of coronary atherosclerosis compared with normotensives, but a higher incidence of LVH. Several mechanisms can account for the increased coronary risk with LVH, including (1) an increase in left ventricular (LV) mass, which by itself requires more oxygen for tissue perfusion; (2) impairment of coronary flow reserve; (3) perivascular fibrosis, which then impairs oxygen supply to the myocardium; and (4) deterioration of LV diastolic function, which hampers myocardial perfusion. Recently, a study reported an impairment of endothelial function and abnormal control of the sympathetic tone in hypertensive patients, which may contribute to the risk of coronary artery disease. In particular, the impaired endothelial function resulting in a prevalence of vasoconstrictive, thrombogenic, and proliferative factors may account for the enhanced ischemic susceptibility of these patients. Furthermore, the cardiac adrenergic system plays an important role in regulating myocardial blood flow. On one hand, hypertensive patients show an exaggerated sympathetic response to physiologic stimuli, whereas on the other hand, the beta-adrenergic receptor-mediated vasodilating component of the sympathetic response is blunted in hypertension. Finally, excess body weight, dyslipidemia, glucose intolerance, and hyperinsulinemia, which are frequently interrelated, represent independent predictors of both coronary artery disease and hypertension.

Early impairment of coronary flow reserve in young men with borderline hypertension

OBJECTIVES

The purpose of this study was to investigate whether functional abnormalities in coronary vasomotion are present in young healthy asymptomatic men fulfilling the World Health Organization (WHO) criteria for borderline hypertension.

BACKGROUND

Previous studies have reported reduced coronary flow reserve in middle-aged subjects with sustained hypertension and hypertension-induced microvascular heart disease or left ventricular hypertrophy.

METHODS

Myocardial blood flow was measured at baseline and during dipyridamole-induced hyperemia by means of positron emission tomography and oxygen-15-labeled water in asymptomatic young men with borderline hypertension (group 1: n = 16, mean +/- SD age 37 +/- 4 years, 24-h ambulatory blood pressure 135 +/- 10/81 +/- 9 mm Hg) and matched healthy control subjects (group 2: n = 19, age 35 +/- 3 years, 24-h ambulatory blood pressure 119 +/- 8/69 +/- 8 mm Hg, p < 0.001). Left ventricular (LV) mass, dimensions and function were measured by echocardiography.

RESULTS

LV mass, dimensions and diastolic function were similar in the study groups. Baseline myocardial blood flow was similar (0.83 +/- 0.21 vs. 0.80 +/- 0.22 ml/g per min, group 1 vs. group 2, respectively, p = NS), and a significant increase in flow was detected after dipyridamole infusion (0.56 mg/kg body weight in 4 min intravenously) in both groups. However, the flow response to dipyridamole was significantly lower in group 1, leading to lower hyperemic flow in group 1 than in group 2 (2.85 +/- 1.20 vs. 3.80 +/- 1.44 ml/g per min, respectively). Consequently, the coronary flow response was lower in hypertensive than in normotensive men (3.46 +/- 1.23 vs. 4.99 +/- 2.5 ml/g per min, group 1 vs. group 2, respectively, p < 0.05).

CONCLUSIONS

These results demonstrate reduced coronary reactivity present in young asymptomatic men with borderline hypertension and no signs of hypertension-induced angina or left ventricular hypertrophy. Because baseline basal myocardial blood flow was unchanged, the reduction in coronary flow reserve depends on an impaired maximal vasodilator capacity.

Changes in myocardial lactate metabolism during ramp exercise in patients with effort angina and microvascular angina

Changes in myocardial lactate metabolism during ramp exercise were investigated through great cardiac vein catheterization in 15 patients with effort angina (EA) and 7 patients with microvascular angina (MVA). The exercise test was performed using a supine bicycle ergometer. Blood samples were obtained from the great cardiac vein (GCV) and the radial artery each minute during exercise. Patients in the EA group showed a point at which the lactate extraction ratio (LER) and the ST level decreased rapidly during exercise. This point was clearly recognized in 12 of 13 patients, and may represent the ischemic threshold. Both the LER and ST level showed similar changes during exercise, and these values were significantly different between the ischemic threshold and peak exercise (p < 0.01). Both the LER and ST level were strongly correlated with the duration of exercise until the threshold (r = 0.703). In the MVA group, both the LER and ST level during exercise continuously decreased throughout exercise without an ischemic threshold in all of the subjects. Endomyocardial biopsy revealed sclerosis of small arteries in the myocardium in all of the patients. In both effort angina and microvascular angina, a close correlation was noted between the change in ST and that in the myocardial lactate extraction ratio.

Myocardial alterations in diabetes and hypertension

Diabetes mellitus is a complex group of diseases that has hyperglycemia as a common metabolic abnormality. Although it is well-known that diabetic patients are susceptible to the effects of large vessel atherosclerosis with specific cardiac and cerebral complications, the association of diabetes mellitus with cardiac dysfunction caused by cardiomyopathy in the absence of significant coronary artery disease has been recognized for many years. However, the pathogenesis of diabetic cardiomyopathy remains unknown and has been somewhat controversial. Specifically, whether diabetes mellitus with its metabolic effects is sufficient to account for cardiomyopathy remains to be proven. This paper reviews the evidence for and against a metabolic etiology. In addition, we review the clinical and experimental evidence that supports the view that diabetes mellitus acts together with hypertension to produce structural damage in the heart that manifests as ventricular dysfunction and ultimately congestive heart failure. The concomitant effects of the metabolic derangements of diabetes and the vascular abnormalities associated with hypertension may lead to microvascular-induced tissue injury. Findings supporting this hypothesis are presented, along with observations suggesting that treatment with vasodilating calcium channel blockers or angiotensin converting enzyme inhibitors may be beneficial in regard to tissue pathology and mortality in experimental models. Recent clinical studies also support a role for the microcirculation in diabetics. Finally, it is suggested that if the microcirculation is pathogenetically involved in diabetic cardiomyopathy, then agents that improve microcirculatory flow along with tight control of hypertension may be as beneficial in the treatment or prevention of diabetic cardiomyopathy as strict metabolic control of hyperglycemia.

Slow coronary flow: clinical and histopathological features in patients with otherwise normal epicardial coronary arteries

Slow flow of dye in epicardial coronary arteries is not an infrequent finding in patients during routine coronary angiography. Whether this pattern of flow can be reversed by nitroglycerin or dipyridamole and whether this angiographic finding is associated with histopathological abnormalities is unknown. We hypothesized that this abnormality could be associated with small vessel disease of the heart, since the epicardial arteries are usually widely patent. Thus, out of the patients undergoing heart catheterization at our institution during the past 5 years, 10 (7%) presented with chest pain, normal epicardial coronary arteries, and abnormal coronary progression of dye. Rest electrocardiogram (ECG), exercise test, echocardiographic examination, and left ventricular angiogram were normal. Coronary angiography showed slow flow of dye on a total of 20 main coronary vessels, that was not reversed by intracoronary nitroglycerin administration. Six of them underwent dipyridamole intravenous infusion that normalized dye run-off in all affected vessels, for a total of 9 main coronary vessels. Histopathological examination (light and electron microscope) of left ventricular endomyocardial biopsies showed thickening of vessel walls with luminal size reduction, mitochondrial abnormalities, and glycogen content reduction. Normal and pathological zones often coexisted in the same specimen. Thus. In some patients with slow coronary flow and patent coronary arteries, functional obstruction of microvessels seems to be implicated, as it is relieved by dipyridamole infusion. Patchy histopathological abnormalities suggestive of small vessel disease are also detectable and could contribute to increase flow resistance.

Systolic ventricular dysfunction and heart failure due to coronary microangiopathy in hypertensive heart disease

Left ventricular hypertrophy in arterial hypertension is characterized by myocyte hypertrophy, myocardial fibrosis, and structural changes of the intramural coronary arteries. Hypertensives with or without left ventricular hypertrophy have a reduced coronary vasodilator reserve due to alterations of the coronary microcirculation. The impairment in coronary vasodilator reserve is likely to initiate a process of malperfusion and malnutrition concomitant with increased metabolic demands. Further, malperfusion is supported by an increase in diastolic filling pressure, which will enhance the extravascular component of coronary resistance. The sum of interactions of these structural alterations of myocardium, interstitium, and coronary vasculature are likely to initiate and maintain a process of myocardial malperfusion and malnutrition, which can provoke functional depression of the myocardial performance, a loss of contractile proteins, an increase in interstitial fibrosis, and, not least, an overall decrease in contractile function in long-standing cardiac hypertrophy. Finally, the reversal of these processes by adequate antihypertensive treatment may contribute to renormalization of cardiac function and to prevention of late cardiac failure in hypertensive heart disease.

Reduced epicardial coronary vasodilator capacity in patients with left ventricular hypertrophy

BACKGROUND

Enlargement of the epicardial coronary arteries occurs in left ventricular (LV) hypertrophy as an adaptation to the increased coronary blood flow.

METHODS AND RESULTS

Vasodilator capacity of the epicardial coronary arteries was determined in 44 patients. The dose-response relation of intracoronary nitroglycerin was assessed in 14 patients (7 control subjects and 7 patients with aortic stenosis [study A]) using quantitative coronary angiography. In a second study (B), vasodilator capacity of the epicardial coronary arteries was determined in 15 control subjects and 15 patients with valvular heart disease. In study A, a curvilinear dose-response relation with maximal vasodilation after 90 micrograms intracoronary nitroglycerin was found in both control subjects and patients with aortic stenosis. Vasodilator capacity was reduced in those with aortic stenosis, although sensitivity to nitroglycerin was similar in both groups. In study B, coronary circumferential length at baseline was larger in those with LV hypertrophy (12.2 +/- 2.2 mm) than in control subjects (8.6 +/- 1.5 mm; P < .001); after 100 micrograms intracoronary nitroglycerin, it increased to 12.9 +/- 2.2 mm (6 +/- 5%) in those with LV hypertrophy and to 10.3 +/- 1.5 mm (21 +/- 8%; P < .001) in control subjects. An inverse relation between baseline circumferential length and its percent increase after nitroglycerin was found (r = -.71, P < .001).

CONCLUSIONS

Vasodilator capacity of the epicardial coronary arteries is reduced in patients with LV hypertrophy, although sensitivity to nitroglycerin is normal. This may be due to a flow-mediated decrease in coronary vasomotor tone and/or the occurrence of vascular remodeling with an enlargement of the coronary arteries.

Structural and functional alterations of the intramyocardial coronary arterioles in patients with arterial hypertension

BACKGROUND

In hypertensive patients with angina pectoris, the coronary vasodilator reserve is frequently impaired despite a normal coronary angiogram. Experimental data indicate that structural alterations of the intramyocardial coronary vasculature contribute to an increased minimal coronary resistance and a diminished coronary flow reserve.

METHODS AND RESULTS

In 14 patients (10 men and 4 women) with arterial hypertension and 8 normotensive subjects, minimal coronary resistance and vasodilator reserve (dipyridamole: 0.5 mg/kg body wt, gas chromatographic argon method) were determined after the angiographic exclusion of relevant coronary artery disease. Coronary reserve was depressed in hypertensive patients (2.7 +/- 2.3 vs 4.6 +/- 1.3, P < or = .05) due to increased minimal coronary resistance (0.64 +/- 30 vs 0.24 +/- 0.055 mm Hg.min.100 g.mL-1, p < or = 0.002). In right septal biopsies, mean external arteriolar diameter (21.6 +/- 2.3 vs 17.2 +/- 2.5 microns, P < or = .001), mean arteriolar wall area (271 +/- 61 vs 172 +/- 62 microns 2, P < or = .01), percent medial wall area (69.9 +/- 4.0 vs 66.0 +/- 3.2%W, P < or = .05), mean periarteriolar fibrosis area (216 +/- 122 vs 104 +/- 68 microns 2, P < or = .05), and volume density of total interstitial fibrosis (3.6 +/- 1.8 vs 1.9 +/- 0.5Vv% fibrosis, P < or = .05) were increased in hypertensive patients compared with normotensive subjects. Minimal coronary resistance correlated with %W (r = .6, P < or = .003) and Vv% fibrosis (r = .62, P < or = .002). Left ventricular mass index (111 +/- 21 vs 97 +/- 17 g/m2, P = NS) and left ventricular end-diastolic pressure (12 +/- 6 vs 8 +/- 3 mm Hg, P = NS) did not correlate significantly with minimal coronary resistance. In multivariate analysis, both %W and Vv% fibrosis explained half of the variability of minimal coronary resistance (r2 = .5, P < or = .002).

CONCLUSIONS

Structural remodeling of the intramyocardial coronary arterioles and the accumulation of fibrillar collagen are decisive factors for a reduced coronary dilatory capacity in patients with arterial hypertension and angina pectoris in the absence of relevant coronary artery stenoses.

Significance of coronary angiography, left heart catheterization, and endomyocardial biopsy for the diagnosis of idiopathic dilated cardiomyopathy

Many physicians assume that a reliable diagnosis of idiopathic dilated cardiomyopathy can be made by noninvasive methods, mainly echocardiography. On the other hand, use of endomyocardial biopsy in those patients who have undergone left heart catheterization and who demonstrate left ventricular dysfunction of unknown origin is increasing. Therefore the purpose of this study was to investigate the yield of that diagnostic strategy in patients with the tentative diagnosis of idiopathic dilated cardiomyopathy. Between 1980 and 1988, 3.2% of our 15,442 patients were diagnosed as having idiopathic dilated cardiomyopathy on the basis of left heart catheterizations and coronary angiograms. Idiopathic dilated cardiomyopathy was diagnosed in 444 patients on the basis of clinical data and results of noninvasive tests before catheterization, but in only 295 of these cases was the diagnosis confirmed by means of coronary angiography and left heart catheterization (predictive value of noninvasive tests is 66%). The remaining 34% of patients demonstrated extensive coronary artery disease (13%), significant valvular heart disease (11%), and other or no heart disease (10%). The diagnostic sensitivity of noninvasive tools (patient history, ECG, stress test, echocardiography) was only 59%. Left heart catheterization can easily be combined with endomyocardial biopsy. With the use of histologic techniques, specific heart muscle diseases were detectable in 3.5% of 209 patients, but in only 1% could therapeutic consequences be determined. Thus coronary angiography and left heart catheterization are mandatory for the correct diagnosis of idiopathic dilated cardiomyopathy.(ABSTRACT TRUNCATED AT 250 WORDS)

The ST segment--the herald of ischaemia, the siren of misdiagnosis, or syndrome X?

Syndrome X is the term applied to patients with anginal-type chest pain who, despite a positive exercise stress test, have angiographically normal coronary arteries. Such patients probably belong to a heterogeneous group, and in a proportion the exercise test is falsely positive. With the availability of more accurate techniques for the detection of myocardial ischaemia, it is apparent that some patients can be shown to develop transient myocardial ischaemia with stress. The paradox of normal coronary arteries and a positive exercise test may be resolved by improved understanding of the regulatory control of regional myocardial blood flow, particularly at the level of the microvasculature, and of the metabolic expression of myocardial ischaemia.

Microvascular angina. Cardiovascular investigations regarding pathophysiology and management

A significant minority of patients with chest pain who undergo cardiac catheterization are found to have angiographically normal coronary arteries. Over the past 25 years, several studies have shown that a subset have demonstrable abnormalities in coronary flow and cardiac function; however, only a minority of these patients have convincing evidence for myocardial ischemia during stress, and alternative mechanisms have been explored to explain the frequent and debilitating symptoms of pain experienced by the majority of these patients undergoing study. Abnormal visceral nociception appears to be a fundamental abnormality in this population, whether or not demonstrable abnormalities in coronary flow or cardiac function can be demonstrated.