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.

Effects of steal-prone anatomy on intraoperative myocardial ischemia. The SPI Research Group.

OBJECTIVES: Our study objective was to determine whether the presence of steal-prone anatomy conferred an increased risk in the development of intraoperative myocardial ischemia. BACKGROUND: Coronary artery steal of collateral blood flow has been demonstrated for many vasodilators, including isoflurane, the most commonly used inhalational anesthetic agent in the United States. It has been postulated that patients with steal-prone anatomy (total occlusion of one coronary artery that is supplied distally by collateral flow from another coronary artery with a > or = 50% stenosis) may be particularly at risk for the development of intraoperative myocardial ischemia when an anesthetic with a vasodilator property is being administered. METHODS: We evaluated the risk of myocardial ischemia under isoflurane anesthesia (vs. a high dose narcotic technique using sufentanil) using continuous intraoperative electrocardiography and transesophageal echocardiography in patients with and without steal-prone anatomy undergoing coronary artery bypass graft surgery. RESULTS: Sixty-two (33%) of the 186 patients had steal-prone anatomy: in 5 (8%) the collateral-supplying vessel was > or = 50% to 69% stenosed, in 24 (39%) it was > or = 70% to 89% stenosed and in 33 (53%) it was > or = 90% stenosed. The incidence of ischemia (transesophageal echocardiography or intraoperative electrocardiography, or both) was similar in patients with and without steal-prone coronary anatomy (18 [29%] of 62 patients vs. 39 [31%] of 124 patients, p = 0.87, 95% confidence interval = -0.13 to 0.17). The incidence of intraoperative ischemia was similar in patients who received isoflurane or sufentanil anesthesia (20 [32%] of 62 patients vs. 37 [30%] of 124 patients, p = 0.87). The incidence of tachycardia and hypotension was low (increases in heart rate = 9.8%, and decreases in systolic blood pressure = 10.8% of total monitoring time during the prebypass period compared with preoperative baseline values). The incidence of adverse cardiac outcome was similar in patients with and without preoperative steal-prone coronary anatomy (4 [7%] of 62 patients vs. 14 [11%] of 124 patients, p = 0.53). CONCLUSIONS: These findings demonstrate that under strict hemodynamic control the presence of steal-prone anatomy does not confer an increased risk in the development of intraoperative myocardial ischemia.

Contrast echocardiography enhances tricuspid but not mitral regurgitation.

Tricuspid regurgitation refers to a systolic leak of blood between the right ventricle and right atrium, across the tricuspid valve. Doppler echocardiographic examination of large numbers of normal individuals has shown that trivial tricuspid regurgitation is extremely common. Measurement of the peak velocity of the regurgitant frequency spectrum on Doppler echocardiography is of considerable clinical importance since it may be used to calculate peak right ventricular and, consequently, peak pulmonary systolic pressure. Doppler recording of the frequency spectrum of a tricuspid regurgitation jet optimally shows a smooth, parabolic, sharply demarcated envelope. In many individuals with trivial tricuspid regurgitation, however, this frequency spectrum is incomplete and its envelope is poorly demarcated. Such inadequate signals do not allow measurement of the spectrum's peak velocity. Like other contrast agents, air-filled microspheres composed of sonicated human serum albumin enhance reflection of Doppler ultrasound and thus have the potential to enhance incomplete tricuspid regurgitation spectra. Furthermore, since sonicated albumin microspheres can cross the pulmonary circulation intact, they have the potential to enhance mitral regurgitation spectra. The purpose of our study was to investigate whether injection of sonicated albumin microspheres enhances incomplete tricuspid and mitral regurgitation frequency spectra to a diagnostic quality. Sonicated albumin microsphere injection enhanced tricuspid regurgitation spectra to optimal quality in 11 of 15 patients (73%). Microsphere injection caused a minor degree of enhancement of the mitral regurgitant spectrum in 1 patient, but did not optimize the spectra in any of 10 patients tested. Saline contrast injection optimally enhanced tricuspid regurgitation spectra in all 8 patients in whom it was used.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of left ventricular contractility using transesophageal echocardiography in patients undergoing coronary artery bypass grafting. The Study of Perioperative Ischemia (SPI) Research Group.

Optimal assessment of left ventricular function requires the use of load-independent indices of myocardial contractility, which often are difficult to obtain in patients undergoing coronary artery bypass graft (CABG) surgery. We have investigated whether the relation between left ventricular end-systolic stress (ESS) (derived from high-fidelity intraventricular pressure measurements and transesophageal-derived wall thickness) and end-systolic area (ESA) (derived from transesophageal echocardiography [TEE]) could provide a load-independent index of left ventricular function. We studied seven men undergoing coronary revascularization. Multiple data points at varied loading conditions were generated for each patient by infusions of sodium nitroprusside and phenylephrine during the period immediately after induction of general anesthesia and preceding surgical incision. While peak systolic blood pressure was pharmacologically altered between 78 and 204 mm Hg, the correlations between ESS and ESA were excellent for all patients (range r = 0.90 to 0.99). Additionally, the slopes of these relations showed a close correlation to their respective baseline thermodilution cardiac indices (r = 0.85, p = 0.02). Appropriate shifts of the ESS/ESA relationships were documented during postextrasystolic potentiation. The authors conclude that the left ventricular ESS/ESA correlation, derived using TEE and intraventricular pressure measurements, may provide a load-independent index of left ventricular inotropic state in patients undergoing CABG surgery.

Isoflurane anesthesia and myocardial ischemia: comparative risk versus sufentanil anesthesia in patients undergoing coronary artery bypass graft surgery. The SPI (Study of Perioperative Ischemia) Research Group.

Whether isoflurane has the potential to produce coronary artery steal and associated myocardial ischemia is still controversial. Previous studies addressing this issue in humans did not purposefully control hemodynamics or use continuous measures of myocardial ischemia. The authors used transesophageal echocardiography (TEE) and continuous Holter electrocardiography (ECG) to study the relative risk of myocardial ischemia during isoflurane or sufentanil anesthesia under strict control of hemodynamics in 186 high-risk patients undergoing elective coronary artery bypass graft (CABG) surgery. Overall, hemodynamics were well controlled (increased heart rate = 9.8%; increased systolic blood pressure = 7.1%; decreased systolic blood pressure = 10.8% of total prebypass time compared with preoperative baseline values), with no difference between the two anesthetics. In the 162 patients with interpretable TEE recordings, moderate to severe TEE ischemic episodes (grade change greater than or equal to 2) developed in 33 (21%) during the prebypass period, with no difference between isoflurane (12 of 56 = 21%) and sufentanil (21 of 106 = 20%) (P = 0.97). The duration and severity of TEE episodes were not significantly different between the two groups. No correlation was observed between TEE ischemic episodes and isoflurane concentrations (range 0.47-1.75%). In the 181 patients with interpretable ECG recordings, ECG evidence of ischemia developed in 34 (19%) during the prebypass period, with no difference between isoflurane (12 of 59 = 20%) and sufentanil (22 of 122 = 18%) (P = 0.87). The duration and severity of electrocardiographic ischemic episodes were also similar in patients receiving either isoflurane or sufentanil. Four of the 62 patients (6%) who received isoflurane had an adverse cardiac outcome versus 15 of 124 patients (12%) who received sufentanil (P = 0.34). The authors' findings demonstrate that, when hemodynamics are controlled, the incidence of myocardial ischemia (TEE or ECG) during isoflurane and sufentanil anesthesia is similar.

Relationship of regional wall motion abnormalities to hemodynamic indices of myocardial oxygen supply and demand in patients undergoing CABG surgery.

To investigate the hemodynamic correlates of perioperative regional wall motion abnormalities (RWMA), we measured wall motion continuously via transesophageal echocardiography (TEE), and related RWMA to continuously measured hemodynamic indices of myocardial oxygen supply and demand (heart rate [HR] and systemic and pulmonary arterial blood pressures). Fifty patients undergoing coronary artery bypass graft (CABG) surgery were studied throughout the prebypass postbypass, and intensive care unit (ICU) periods. Only 28% of TEE episodes (RWMA suggestive of ischemia) were preceded by acute changes in any hemodynamic parameter. Specifically, 7% of TEE episodes were preceded by increases in HR (20% deviation from control), 14% by increases in systolic blood pressure (SBP), 13% by decreases in diastolic blood pressure (DBP), and 9% by increases in pulmonary artery diastolic pressure (PAD). Twelve per cent of TEE episodes were associated with increases in rate-pressure product (RPP) to greater than 12,000, and 27% were associated with decreases in mean arterial pressure (MAP)/HR to less than 1 at the onset of TEE episodes. Comparison among periods revealed that postbypass TEE episodes were more frequently associated with either increases in demand or decreases in supply than were prebypass episodes (53% vs. 25%, P less than 0.05). ECG ischemic episodes also were infrequently (30%) associated with acute changes in HR, SBP, DBP, or PAD. We conclude that perioperative TEE episodes are infrequently triggered by changes in hemodynamics, suggesting that a primary decrease in myocardial oxygen supply may be an important mechanism for most perioperative RWMA. In addition, neither pulmonary artery catheter pressure measurements nor specialized indices (RPP and MAP/HR) appear to be useful in predicting TEE episodes.

Coronary morbidity and mortality, pre-existing silent coronary artery disease, and mild hypertension.

Experimental findings in animals and epidemiologic studies in humans provide strong evidence that hypertension promotes the onset and progression of atherosclerosis. However, effective antihypertensive therapy has not consistently reduced the incidence of cardiac events in the major trials of treatment for mild hypertension. In reviewing these trials and the recent data on the pathophysiologic interrelationships among hypertension, atherosclerosis, and myocardial ischemia, two factors stand out: First, the power of these trials to produce a positive result was limited because of their size, entry criteria, duration, and other considerations; second, autopsy and epidemiologic data suggest that some patients in these trials probably had advanced coronary artery disease at the time of entry. Because these patients probably developed symptomatic coronary artery disease by virtue of this pre-existing disease, the failure of antihypertensive therapy alone to prevent cardiac events in trials of relatively short duration should not be construed as evidence against its value as a long-term therapy.

Hypertensive heart disease: the critical role of left ventricular hypertrophy.

The presence of left ventricular hypertrophy in hypertensive patients has been linked with increased likelihood for developing congestive heart failure, the potential for myocardial ischemia and the inherent risk for sudden death. In this paper we review current knowledge regarding the role of left ventricular hypertrophy in cardiac morbidity and mortality and emphasize the need for further study to explore the efficacy of pharmaceutical agents in reducing cardiac complications of hypertension in high-risk patients.