Usefulness of thallium-201 scintigraphy in predicting the development of angina pectoris in hypertensive patients with left ventricular hypertrophy

Hypertensive patients with false-positive thallium-201 scintigraphic results in the infero-posterior wall are in high risk for coronary artery disease development

BACKGROUND

It has been previously postulated that Thallium-201 (Tl201) scintigraphy is characterized by relatively low specificity in hypertensive patients. This study was undertaken to assess any possible influence of false-positive scintigraphic results on the prognosis of hypertensive patients.

METHODS

The study group comprised 179 consecutive hypertensive patients (128 men and 51 women), aged 50+/-7 years, who underwent exercise Tl(201) scintigraphy and coronary angiography (patients with normal scintigraphic results underwent coronary angiography due to persistent angina-like symptoms). All patients with normal coronary arteries underwent a second Tl201 scintigraphy within 36+/-6 months. Patients with reversible ischemia in the second scintigraphy underwent also a second coronary angiography.

RESULTS

Coronary artery disease (CAD) was detected in 78 (44%) patients, while the rest 101 (56%) patients had normal coronary arteries. Abnormal scintigraphic results were revealed in 66 (85%) patients with CAD and in 38 (38%) patients without CAD. Twenty-two (58%) of the 38 hypertensive patients with false-positive scintigraphic results presented reversible ischemia of the infero-posterior wall of the left ventricle. Coronary artery disease was detected in 7 (32%) of these patients during the follow-up period.

CONCLUSIONS

Hypertensive patients with normal coronary arteries and false-positive scintigraphic results usually present with reversible ischemia of the infero-posterior wall of the left ventricle. This group of patients seems to be at increased risk of developing CAD in a long-term follow-up period.

State of the Art lecture. Risk mechanisms in hypertensive heart disease

In this report, some of the underlying pathophysiological alterations associated with the independent risk from hypertensive heart disease and left ventricular hypertrophy are discussed. Emphasized are the classically described coronary hemodynamic alterations of decreased coronary blood flow and flow reserve with increased coronary vascular resistance and minimal coronary resistance; more recent concepts of endothelial dysfunction are emphasized. Additionally, increased collagen deposition within the ventricular walls and perivascularly participates importantly. These changes are exacerbated by the aging process and perhaps by increased dietary salt intake. Consequences of these functional and structural changes include further endothelial dysfunction, impairment of coronary hemodynamics, and ventricular contractile function (diastolic as well as systolic). The clinical consequences of these alterations are angina pectoris (with or without atherosclerosis), myocardial infarction, cardiac failure, lethal dysrhythmias, and sudden cardiac death. Thus, not all that is clinically recognized as "left ventricular hypertrophy" is true myocytic hypertrophy with structural remodeling; other important comorbid changes occur that directly affect risk, including ventricular fibrosis, impaired coronary hemodynamics, and endothelial dysfunction.

Hypertension and coronary artery disease

Hypertension is one of the major risk factors for coronary artery disease. This risk is considerably magnified by the presence of left ventricular hypertrophy. The likeliest dominant factor in this increased risk is myocardial ischaemia, the recognition of which is of key importance. Antihypertensive agents ideally should also protect against occurrence of the clinical syndromes associated with coronary artery disease.

Detection of coronary artery disease in the presence of left ventricular atrophy

To evaluate the accuracy of exercise echocardiography for the recognition of coronary artery disease in the presence of left ventricular hypertrophy 70 patients were studied. Significant coronary artery disease was present in 25 patients and left ventricular hypertrophy had 29 patients. All patients underwent an exercise ECG and echocardiographic test during which cine-loop digitized echocardiography was obtained. Wall motion was analyzed and a regional wall motion score index was calculated. The overall sensitivities of exercise ECG and echocardiography for detecting coronary artery disease were 60% and 64%, respectively, and the specificities were 49% and 78%, respectively. In patients with left ventricular hypertrophy the specificity of exercise echocardiography was higher (71%) compared to exercise ECG (21%) while in patients without hypertrophy the sensitivity was higher (70% vs. 40%, respectively). Of the 19 patients with a non-diagnostic stress ECG, echocardiography correctly identified 100% of those with coronary artery disease but only 53% of those without disease. It is concluded that exercise digital echocardiography represents a good diagnostic alternative to the exercise ECG for identifying coronary artery disease in the presence of left ventricular hypertrophy and should be useful in patients with a non-diagnostic exercise ECG.

Diagnostic usefulness of postexercise systolic blood pressure response for detection of coronary artery disease in patients with electrocardiographic left ventricular hypertrophy

Patients with left ventricular (LV) hypertrophy often have a positive result on exercise testing despite a normal coronary arteriogram. This indicates that exercise-induced ST depression is not always an accurate indicator of the presence of coronary artery disease (CAD) in such patients. We evaluated the usefulness of the postexercise systolic blood pressure (BP) response for detection of CAD in 51 patients with both electrocardiographic evidence of LV hypertrophy and positive ST depression on treadmill exercise testing. Coronary cineangiograms showed normal coronary arteries in 23 patients (45%) (group 1) and significant CAD in 28 patients (55%) (group 2). The systolic BP ratio (systolic BP at 3 minutes of recovery divided by systolic BP at peak exercise) was significantly higher in group 2 than in group 1 (1.01 +/- 0.19 vs 0.80 +/- 0.09; p < 0.001). Analysis of the relative cumulative frequency revealed that a systolic BP ratio of 0.86 was the cutoff point for distinguishing a patient with CAD from one with normal coronary arteries. The sensitivity, specificity, and accuracy of a systolic BP ratio > or = 0.86 for detection of CAD in patients with LV hypertrophy were 79%, 83%, and 82%, respectively. Our results suggest that the use of an abnormal BP ratio, in combination with ST depression, improves the accuracy of treadmill exercise testing for detecting CAD in patients with electrocardiographic evidence of LV hypertrophy.

Cardiac and arterial hypertrophy and atherosclerosis in hypertension

Clinical evaluation of the hypertensive patient has traditionally relied on physician measurement of blood pressure and assessment of target-organ involvement by simple laboratory tests. However, this approach is limited in its ability to identify individual patients at high or low risk of complications. In recent years, noninvasive methods have been developed to identify pathological transformations of the heart and arteries that collectively comprise "preclinical hypertensive disease." Measurements by echocardiogram or other methods of left ventricular mass and relative wall thickness identify a spectrum of cardiac adaptations to hypertension, including concentric and eccentric hypertrophy, the recently described pattern of "concentric left ventricular remodeling" (normal mass but increased relative wall thickness), and normal ventricular geometry. In clinical studies, each anatomic pattern is associated with a distinct profile of resting hemodynamics, ambulatory blood pressure, myocardial contractility, and risk of adverse outcomes. Ultrasonic imaging of the carotid or other arteries makes it possible to detect increased arterial wall thickness and discrete atheromas noninvasively. Carotid wall thickness and lumen diameter parallel similar ventricular dimensions in normotensive and hypertensive humans, indicating the presence of integrated patterns of cardiac and vascular adaptation to hypertension. Furthermore, peripheral atherosclerosis is associated with higher ventricular mass and a more adverse 24-hour blood pressure profile. In summary, noninvasive visualization of the heart and blood vessels reveals a spectrum of patterns of anatomic and functional adaptations that are related to the pathophysiology and prognosis of hypertension.

Scintigraphic and electrocardiographic evidence of silent coronary artery disease in asymptomatic hypertension: a case-control study

OBJECTIVES

This study was conducted to determine the incidence of physiologically significant coronary artery disease in a group of asymptomatic high risk men with essential hypertension and to assess the validity of noninvasive tests in a subset of these patients undergoing coronary arteriography.

METHODS

Two hundred twenty-six asymptomatic men (mean age 61 +/- 8 years) with essential hypertension and no clinical evidence of coronary artery disease but with at least one additional coronary risk factor were studied prospectively. Fifty age- and risk factor-matched normotensive subjects were evaluated as a control group. After a minimum of 4 days without medication, subjects underwent stress thallium-201 scintigraphy, exercise and 48-h ambulatory electrocardiography, and echocardiography. Coronary angiography was performed in a subset of 34 (40%) of 84 patients with one or more positive test results.

RESULTS

A positive thallium-201 scintigram (18% vs. 6%; odds ratio 3.4, confidence interval 0.95 to 10.8, p = 0.056), exercise electrocardiograms (ECGs) (37% vs. 13%; odds ratio 4.1, confidence interval 1.5 to 11.2, p < 0.003) and ambulatory ECG (15% vs. 0%, p < 0.05) were more common in the hypertensive group than in the control group. In the cohort undergoing coronary angiography, thallium-201 scintigraphy was both sensitive and specific for epicardial atherosclerotic coronary disease (90% and 79%, respectively), but positive exercise and ambulatory ECGs occurred frequently in the absence of significant coronary stenoses. In the 39% of hypertensive patients who had mild to moderate left ventricular hypertrophy, positive exercise and ambulatory ECGs occurred at a higher rate.

CONCLUSIONS

These findings suggest that physiologically significant coronary artery disease occurs more frequently in asymptomatic hypertensive men than in comparable normotensive control subjects. In the subgroup undergoing coronary arteriography, reversible scintigraphic defects were both sensitive and specific for diagnosing epicardial coronary artery disease, but exercise and ambulatory ECGs appeared to yield frequent false positive results, especially when left ventricular hypertrophy was present. These results indicate that patients with "silent" coronary artery disease can be identified among high risk hypertensive patients, but the appropriate application of such screening in clinical practice remains to be determined.

Symptomatic and silent myocardial ischaemia in hypertensive patients with left ventricular hypertrophy

OBJECTIVE

To assess the prevalence of symptomatic and silent myocardial ischaemia in patients with hypertensive left ventricular hypertrophy.

DESIGN

Cross sectional study.

SETTING

University department of medical cardiology.

PATIENTS

90 patients (68 men and 22 women; mean age 57 (range 25 to 79)) with left ventricular hypertrophy due to essential hypertension.

INTERVENTIONS

48 hour ambulatory ST segment monitoring (all patients), exercise electrocardiography (n = 79), stress thallium scintigraphy (n = 80), coronary arteriography (n = 35).

RESULTS

43 patients had at least one episode of ST segment depression on ambulatory electrocardiographic monitoring. The median number of episodes was 16 (range 1 to 84) with a median duration of 8.6 (range 2 to 17) min. Over 90% of these episodes were clinically silent. 26 patients had positive exercise electrocardiography and 48 patients had reversible thallium perfusion defects despite chest pain during exercise in only five patients. 18 of the 35 patients who had coronary arteriography had important coronary artery disease. Seven of these patients gave no history of chest pain.

CONCLUSIONS

Symptomatic and silent myocardial ischaemia are common in hypertensive patients with left ventricular hypertrophy, even in the absence of epicardial coronary artery disease.

Left ventricular hypertrophy in hypertension

Major advances in left ventricular hypertrophy (LVH) and hypertension have occurred in recent years. The ability to diagnose LVH has been improved by echocardiography, and with this technique it has been shown that evidence of LVH is an important independent risk factor for cardiovascular disease. The major cause of death in patients with hypertension and LVH is coronary artery disease. Therefore an understanding of the interrelationships between these two disorders is fundamental, and it is now clear that the hypertrophied ventricle is vulnerable to myocardial ischemia. Appreciation of the mechanisms of sudden death has also increased, although the exact situation in patients with LVH remains to be clarified. Regression of LVH is known to occur with the use of several different antihypertensive drugs. Recent studies indicate that the calcium blocking agent nicardipine, in addition to beta-blocking drugs and angiotensin-converting enzyme inhibitors, brings about LVH regression without any deterioration of left ventricular function. However, further studies are needed to assess the long-term benefits of this regression.