Pulmonary hypertension: a cellular basis for understanding the pathophysiology and treatment.

Much of the understanding of hypertensive pulmonary vascular disease comes from studies of primary pulmonary hypertension. The three subtypes of primary pulmonary hypertension, plexogenic pulmonary arteriopathy, thromboembolic pulmonary hypertension and venoocclusive disease, have served as a basis to understand the mechanisms and to develop treatments of all forms of pulmonary hypertension. However, many inconsistencies regarding presumed pulmonary vasoconstriction and recurrent embolization remain. With newer data on the influence of the endothelium on vascular responsiveness and thrombosis, it appears that older concepts regarding the pathophysiology of pulmonary hypertension need to be revised. Recent studies have shown that plexogenic pulmonary arteriopathy is associated with abnormalities of endothelial structure and function that could result in impaired release of endothelial derived relaxing factors. Thromboembolic pulmonary arteriopathy, or more properly thrombotic pulmonary hypertension, appears to be the result of endothelial cell injury that creates a procoagulant environment in the pulmonary vascular bed with the development of widespread eccentric intimal proliferation and thrombosis in situ. It is possible that the effectiveness of vasodilator or anticoagulant therapy depends on the nature of the endothelial injury. Secondary pulmonary hypertension without endothelial injury, such as that which occurs with hypoxic lung disease or mitral stenosis, appears more satisfactorily treated when the primary cause is reversed.

Doppler echocardiographic assessment of impaired left ventricular filling in patients with right ventricular pressure overload due to primary pulmonary hypertension.

In patients with primary pulmonary hypertension, competition between the right and left ventricles for the limited pericardial space results in distortion of left ventricular geometry reflected in displacement of the ventricular septum toward the left ventricular cavity. Left ventricular shape is most dramatically deranged at end-systole and early diastole, suggesting the possibility that the distribution of left ventricular diastolic filling might be altered. To investigate this hypothesis, nine patients with primary pulmonary hypertension and nine normal individuals were studied with echocardiographic techniques. Left ventricular isovolumic relaxation time was significantly prolonged in patients with primary pulmonary hypertension by comparison with normal individuals (129 +/- 36 versus 53 +/- 9 ms, p less than 0.005) and the fraction of the transmitral flow velocity integral occurring in the first half of diastole was significantly less than in normal individuals (38 +/- 14% versus 70 +/- 9%, p less than 0.005). Measurement of fractional changes in short-axis left ventricular cavity area similarly demonstrated that in patients with primary pulmonary hypertension fractional early diastolic cavity expansion (32 +/- 11%) was significantly less than in normal individuals (78 +/- 9%, p less than 0.005). In patients with primary pulmonary hypertension, the ventricular septum was abnormally flattened toward the left ventricular cavity at end-systole (normalized septal curvature 0.04 +/- 0.19) and remained that way throughout early diastolic filling but returned toward normal at end-diastole (normalized septal curvature 0.68 +/- 0.19, p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Doppler echocardiographic demonstration of the differential effects of right ventricular pressure and volume overload on left ventricular geometry and filling.

To compare the effects of isolated right ventricular pressure and volume overload on left ventricular diastolic geometry and filling, 11 patients with primary pulmonary hypertension, 11 patients with severe tricuspid regurgitation due to tricuspid valve resection and 11 normal subjects were studied with use of Doppler echocardiographic techniques. Right ventricular systolic overload in primary pulmonary hypertension resulted in substantial leftward ventricular septal shift that was most marked at end-systole and early diastole and decreased substantially by end-diastole. Right ventricular diastolic overload after tricuspid valve resection resulted in maximal leftward ventricular septal shift at end-diastole sparing end-systole and early diastole. The early diastolic distortion of left ventricular geometry associated with right ventricular pressure overload resulted in prolongation of isovolumetric relaxation of the left ventricle (129 +/- 39 ms) and a reduction in early diastolic filling compared with values in normal subjects. Late diastolic distortion of left ventricular geometry associated with right ventricular volume overload had no influence on the duration of left ventricular isovolumetric relaxation (52 +/- 32 ms) but caused a reduction in the atrial systolic contribution to late diastolic filling of the left ventricle compared with values in normal subjects. In patients with right ventricular pressure overload, 52 +/- 16% of left ventricular filling occurred in early diastole compared with 78 +/- 11% in patients with right ventricular volume overload (p less than 0.001). The differential effects of systolic and diastolic right ventricular overload on the pattern of left ventricular filling appear to be related to the timing of leftward ventricular septal displacement.

Improved regional ventricular function after successful surgical revascularization.

Left ventricular segments with reversible asynergy at rest demonstrate reversible myocardial perfusion defects on exercise thallium-201 scintigrams. To determine if improved perfusion eliminates asynergy at rest, 23 patients with angina (stable in 21, unstable in 2) were studied before and after coronary artery bypass surgery. All patients underwent exercise myocardial perfusion scintigraphy, contrast ventriculography and coronary arteriography before and after surgery. Selective graft angiography was performed during the postoperative catheterization to determine graft patency. Segmental ventricular function was quantitated by a regional fraction method. The scintigrams were divided into five regions and compared with the corresponding regions of the ventriculogram. Seventy-one of a possible 142 ventricular segments exhibited exercise-induced perfusion deficits. Preoperative regional ejection fraction was normal in 42 of these segments and abnormal in 29. Postoperatively, in 19 of the abnormal segments, function improved or normalized. All these segments had improved perfusion during exercise after surgery and were supplied by a patent bypass graft. Nine of the 10 segments in which abnormal wall motion persisted postoperatively continued to have exercise-induced perfusion deficits, and 9 of the 10 segments were supplied by an occluded or stenotic graft or one with poor run off. Of the 42 segments with normal wall motion preoperatively, 30 had improved perfusion after surgery and 35 maintained normal function. This study indicates that asynergy at rest is permanently reversed after coronary bypass surgery if improved myocardial perfusion can be documented. These findings are consistent with but do not prove the concept that reversible rest asynergy may reflect chronic ischemia or a prolonged effect from previous ischemic episodes.

Reproducibility of left ventricular myocardial volume and mass measurements by ultrafast computed tomography.

Ultrafast computed tomography has been reported to be an accurate method of measuring left ventricular mass in dogs. To assess the interstudy, intraobserver and interobserver variability of left ventricular myocardial mass measurements in humans, left ventricular myocardial volume was measured three times within 24 h in 16 patients with ischemic heart disease. The mean percent difference of the mean of the three studies performed was -0.01 +/- 1.4% (range -2.9% to 3.6%). The regression analysis for the intraobserver variability at baseline was: Y = -4.33 + 1.03X; r = 0.99, SEE = 3.5 ml. The mean percent difference of the mean of the two sets of measurements performed by two independent observers was 0.28 +/- 2.1% (range -4.35% to 4.35%). The interobserver variability excluding papillary muscles at baseline study was: Y = -4.34 + 1.06X; r = 0.99, SEE = 1.5 ml. The regression analysis with versus without papillary muscles showed: Y = -8.72 + 0.97X; r = 0.96, SEE = 2.6 ml. Regression analysis to assess the variability of 24-h studies at end-systole versus end-diastole revealed: Y = 3.07 + 0.94X; r = 0.97, SEE = 1.8 ml. In conclusion, ultrafast computed tomography is a minimally invasive technique, with very low interstudy, intraobserver and interobserver variability for left ventricular myocardial volume and mass determinations in serial studies.

Antinuclear antibodies in primary pulmonary hypertension.

The association of positive antinuclear antibodies with the clinical and hemodynamic features of 43 patients with primary pulmonary hypertension and 16 patients with secondary pulmonary hypertension was investigated. Each patient had determinations of antinuclear antibodies using a KB cell substrate immunofluorescent test. Of the patients with primary pulmonary hypertension, 40% had positive antinuclear antibodies at titers of 1:80 dilutions or greater. There were no differences between patients with primary pulmonary hypertension and positive antinuclear antibodies compared with those with negative antinuclear antibodies in relation to clinical or hemodynamic status. A 6% incidence rate of antinuclear antibodies was found in patients with secondary pulmonary hypertension, similar to that in the normal population. The clinical, hemodynamic, serologic and histologic similarity between patients with primary pulmonary hypertension and those with unexplained pulmonary hypertension associated with collagen vascular disorders suggests that primary pulmonary hypertension in some patients may represent a collagen vascular disease confined to the lungs. The frequency of positive antinuclear antibody tests would place primary pulmonary hypertension between rheumatoid arthritis and scleroderma in the spectrum of collagen vascular diseases. Further studies are necessary, however, before one might expect that immunosuppressive therapy would be beneficial to these patients.

Screening patients with chest pain in the emergency department using electron beam tomography: a follow-up study.

OBJECTIVES: The high sensitivity of electron beam tomography (EBT) in the detection of coronary artery calcium (CAC) and obstructive coronary artery disease prompted us to investigate the association between CAC detection and future cardiac events in patients with acute chest pain syndromes requiring hospitalization. BACKGROUND: Three studies have documented that EBT is a rapid and efficient screening tool for patients admitted to the emergency department (ED) with chest pain, but there is a paucity of long-term follow-up data on these chest pain patients. METHODS: We conducted a prospective observational study of 192 patients admitted to the ED of a large tertiary care hospital for chest pain syndromes. Upon admission, patients underwent EBT scanning in addition to the usual care for chest pain syndromes. During the 17-month enrollment period, 221 patients were scanned (54% men with a mean age of 53 +/- 9 years). Average follow-up was 50 +/- 10 months using chart review. RESULTS: Fifty-eight patients had coronary events confirmed by a blinded medical record review. The presence of CAC (a total calcium score >0) and increasing score quartiles were strongly related to the occurrence of hard cardiac events including myocardial infarction and death (p < 0.001) and all cardiovascular events (p < 0.001). Stratification by age- and gender-matching further increased the prognostic ability of EBT (for scores above vs. below the age- and gender-matched CAC scores; odds ratio: 13.1, 95% confidence intervals: 5.62, 35.9). CONCLUSIONS: These data support previous reports demonstrating that the presence of CAC in a symptomatic cohort is a strong predictor of future cardiac events. This study supports the use of EBT in a symptomatic cohort with prompt discharge of those patients with negative scans. Furthermore, the absence of CAC is associated with a very low risk of future cardiac risk events in this population over the subsequent seven years (annual event rate <1%).

Evaluation of early postoperative coronary artery bypass graft patency by contrast-enhanced computed tomography.

Fifty patients with 117 coronary bypass grafts were studied by contrast-enhanced computed tomography at an average of 5 +/- 4 days after surgery to determine if this technique was a feasible method for detecting early postoperative graft occlusion. The study was limited in only three patients because of incisional chest pain (one patient) or multiple metal clips attached to the graft (two patients). The distal patency of sequential grafts cannot be determined by current techniques. There was a lower graft patency rate (70%) in the 10 patients with perioperative myocardial infarction than in the 40 (95%) without (p less than 0.025), but most regions of infarcted myocardium were perfused by patent grafts. There were eight graft occlusions in eight patients. The graft occlusion rate (30%) was significantly higher (p less than 0.025) in grafts with intraoperative flows less than 45 ml/min. The postoperative complications of myocardial dysfunction, arrhythmia and coronary artery spasm did not correlate with graft occlusion. Early graft occlusion is uncommon (7%) and usually occurs in grafts with low flows or severe distal disease (seven of eight grafts), or both. Thus, the need for early reoperation is very infrequent. It is concluded that contrast-enhanced computed tomography is feasible for the assessment of coronary bypass graft patency. Because early graft occlusion is unusual the technique may be an ideal noninvasive screening method.

Congenital aneurysm of the left sinus of Valsalva with an aortopulmonary tunnel.

Aneurysm of the left sinus of Valsalva is rare, and there is only one previous report of rupture into the pulmonary artery. This report describes a patient with valvular pulmonary atresia and ventricular septal defect in whom a portion of his pulmonary blood flow was supplied by an aortopulmonary tunnel arising from a left sinus of Valsalva aneurysm. The surgical implications of precise definition of the type of aortopulmonary communication are discussed.

Exercise ultrafast computed tomography for the detection of coronary artery disease.

Ultrafast computed tomography permits the assessment of global and regional left ventricular function during exercise. To evaluate the feasibility of using this new technique for the diagnosis of coronary artery disease, 27 patients undergoing cardiac catheterization for diagnosis of chest pain were evaluated. Fifteen patients had significant (greater than 50%) coronary artery stenosis by quantitative coronary angiography. One vessel disease was found in 12 patients and multivessel disease in 3. Fourteen (93%) of the 15 patients with significant coronary stenosis had a decrease in ultrafast computed tomographic ejection fraction during exercise from (mean +/- SD) 65 +/- 7% to 60 +/- 7% (p less than 0.001). The tomographic ejection fraction increased greater than 5% units during exercise in 10 (83%) of the 12 patients with normal coronary arteries. The mean tomographic ejection fraction in this group was 68 +/- 6% at rest and 75 +/- 6% at peak exercise (p less than 0.001). Regional wall motion was quantified by analyzing the segmental ejection fraction of 12 30 degree pie segments at each tomographic level of the left ventricle. A new regional wall motion abnormality developed during exercise in 12 (86%) of 14 patients with coronary artery disease; one patient was excluded because of a technical problem in data storage. Eleven (93%) of the 12 patients with normal coronary arteries had normal wall motion during exercise. In no patient with ischemic heart disease were both variables, ejection fraction response and regional wall motion, normal. Exercise ultrafast computed tomography appears to be a useful technique for the evaluation of coronary artery disease in patients with chest pain and predominant single vessel coronary artery disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Responses to constant work rate bicycle ergometry exercise in primary pulmonary hypertension: the effect of inhaled nitric oxide.

OBJECTIVES: The purpose of this study was to investigate the responses of patients with primary pulmonary hypertension (PPH) to constant work rate exercise and to examine the effect of nitric oxide (NO) inhalation. BACKGROUND: Maximal exercise tolerance is reduced in PPH, but gas exchange responses to constant work rate exercise have not been defined. We hypothesized that increased pulmonary vascular resistance in PPH would reduce the rate of rise of minute oxygen consumption in response to a given work rate. Because NO may lower pulmonary vascular pressures in PPH, we also postulated that inhaled NO might ameliorate gas exchange abnormalities. METHODS: Nine PPH patients and nine matched normal subjects performed 6-min duration constant work rate cycle ergometry exercise (33.9+/-13.4 W). Patients performed two experiments: breathing air and breathing air with NO (20 ppm). Preexercise right ventricular systolic pressure was assessed by Doppler echocardiography. Normal subjects performed the air experiment only. Gas exchange and heart rate responses were characterized by fitting monoexponential curves. RESULTS: In PPH patients, resting right ventricular systolic pressure fell after NO inhalation (from 83.8+/-16.9 to 73.9+/-21.6 mm Hg, p<0.01, analysis of variance with Tukey correction), but not after breathing air alone (from 88.0+/-20.8 to 86.7+/-20.6 mm Hg, p = NS). Nitric oxide did not affect any of the gas exchange responses. Minute oxygen consumption was similar by the end of exercise in patients and normals, but increased more slowly in patients (mean response time [MRT]: air, 63.17+/-14.99 s; NO, 61.60+/-15.45 s) than normals (MRT, 32.73+/-14.79, p<0.01, analysis of variance, Tukey test). Minute oxygen consumption kinetics during recovery were slower in patients (MRT air: 82.50+/-29.94 s; NO, 73.36+/-15.87 s) than in normals (MRT, 34.59+/-7.11 s, p<0.01). Heart rate kinetics during exercise and recovery were significantly slower in patients than in normals. CONCLUSIONS: The cardiac output response is impaired in PPH. Nitric oxide lowered pulmonary artery pressure at rest, but failed to improve exercise gas exchange responses.

Graft patency in patients with coronary artery bypass operation complicated by perioperative myocardial infarction.

Coronary artery bypass graft patency was examined by contrast-enhanced computed tomography in 18 patients with perioperative myocardial infarction soon after surgery to determine the role of graft occlusion. Preoperative coronary angiograms were reviewed to assess native coronary disease and visible collateral channels in the distribution of the myocardial infarction. Perioperative myocardial infarction was diagnosed if creatine kinase-MB was elevated, characteristic electrocardiographic changes occurred and, in the majority of cases, the pyrophosphate scan was positive. Fourteen patients (78%) had patent grafts and perioperative myocardial infarction in the distribution of the grafted vessel. Four patients had an occluded graft with infarction in the distribution of the grafted vessel. Among the 14 patients with patent grafts, there was a significant difference (p less than 0.0005) in the degree of the mean (+/- standard deviation) diameter stenosis of 80 +/- 11% in native coronary vessels supplying the perioperatively infarcted myocardium versus a 55 +/- 12% mean diameter stenosis in the 23 bypassed native coronary vessels supplying noninfarcted myocardium. It is concluded that the majority of perioperative myocardial infarcts associated with coronary artery bypass operations are not caused by graft occlusion. The severity of coronary obstruction in the grafted vessel and the lack of collateral vessels to the region of perioperative infarction in patients with patent grafts suggests that an island of jeopardized myocardium exists that is subject to inadequate intraoperative preservation.

Prognostic significance of cardiac cinefluoroscopy for coronary calcific deposits in asymptomatic high risk subjects.

OBJECTIVES: This research investigated the prognostic significance of radiographically detectable coronary calcific deposits. BACKGROUND: Coronary calcific deposits are almost always associated with coronary atherosclerosis. We investigated the association between fluoroscopically determined coronary calcium and coronary heart disease end points at 1 year of follow-up. METHODS: This prospective population-based cohort study was conducted in the suburbs of Los Angeles. Fourteen hundred sixty-one asymptomatic adults with an estimated > or = 10% risk of having a coronary heart disease event within 8 years underwent cardiac cinefluoroscopy for assessment of coronary calcium at initiation of the study. Clinical status including angina, documented myocardial infarction, myocardial revascularization and death from coronary heart disease were determined after 1 year. RESULTS: The prevalence of calcific deposits was high (47%). A follow-up examination at 1 year was successfully completed in 99.9% of subjects. Six subjects (0.4%) had died from coronary heart disease and 9 (0.6%) had had a nonfatal myocardial infarction. Thirty-seven subjects (2.5%) reported angina pectoris, and 13 (0.9%) had undergone myocardial revascularization. Fifty-three subjects had at least one event during the 1-year period. Radiographically detectable calcium was associated with the presence of at least one of these end points, with a risk ratio of 2.7 (confidence limits 1.4, 4.6). The presence of coronary calcium was an independent predictor of at least one end point when controlling for age, gender and risk factors. However, three deaths due to coronary heart disease and two nonfatal myocardial infarctions occurred in subjects without detectable coronary calcium. CONCLUSIONS: The presence of coronary calcific deposits incurs an increased risk of coronary heart disease events in asymptomatic high risk subjects at 1 year. This increased risk is independent of that incurred by standard risk factors.

Primary pulmonary hypertension: improved long-term effects and survival with continuous intravenous epoprostenol infusion.

OBJECTIVES: This study sought to determine the long-term effects of continuous infusion of epoprostenol (epo) therapy on survival and pulmonary artery pressure in patients with primary pulmonary hypertension (PPH). BACKGROUND: PPH is a progressive disease for which there are few effective therapies. METHODS: Patients with PPH and New York Heart Association functional class III or IV symptoms of congestive heart failure underwent right heart catheterization and Doppler-echocardiography to measure the maximal systolic pressure gradient between the right ventricle and right atrium (delta P) and cardiac output (CO). Doppler-echocardiography and catheterization data were compared. Patients were followed up long term with Doppler-echocardiography. RESULTS: Of 69 patients who went on to receive epo, 18 were followed up for > 330 days (range 330 to 700). During long-term follow-up, there was a significant reduction in delta P, which decreased from 84.1 +/- 24.1 to 62.7 +/- 18.2 (mean +/- SD, p < 0.01). A Kaplan-Meier plot of survival of our study patients demonstrated improved survival compared with that of historical control subjects. The 1-, 2- and 3-year survival rates for our patients were 80% (n = 36), 76% (n = 22) and 49% (n = 6) compared with 10- (88%, n = 31), 20- (56%, n = 27) and 30-month (47%, n = 17) survival rates in historical control subjects. CONCLUSIONS: Patients receiving continuous infusion of epo for treatment of PPH experience a decrease in pulmonary artery pressure. Long-term follow-up of this single-center patient group demonstrated improved long-term survival during epo therapy compared with that in historical control subjects and confirms predicted improved outcomes based on shorter follow-up periods.

Usefulness of electron beam computed tomography scanning for distinguishing ischemic from nonischemic cardiomyopathy.

OBJECTIVES: This study was undertaken to evaluate the ability of electron beam computed tomography (EBCT) to distinguish ischemic from nonischemic causes of cardiomyopathy by evaluating heart failure patients for coronary calcification (CC). BACKGROUND: The etiology of heart failure, whether coronary-induced or nonischemic, may be difficult to discern clinically. Differentiation of ischemic from nonischemic etiology is clinically important for both therapeutic and prognostic implications. With its ability to noninvasively discern and quantitate coronary artery calcification, EBCT correlates well with angiographic stenosis and thus may be useful in distinguishing ischemic and nonischemic cardiomyopathies. METHODS: One hundred and twenty-five patients with cardiomyopathy (ejection fraction <0.40) and known coronary anatomy underwent EBCT coronary scanning to evaluate for CCs within 3 months of coronary angiography. RESULTS: Of the 72 patients who were found to have ischemic cardiomyopathy, 71 patients had CC by EBCT (sensitivity 99%, p < 0.001), mean score 798+/-899. In comparison, among the 53 patients without significant coronary artery disease (CAD) (nonischemic cardiomyopathy), the mean score was significantly lower (17+/-51; p < 0.0001), and 44 patients had a CC score of 0 (no CC present). The specificity of EBCT to exclude CAD in patients with cardiomyopathy was 83%, using a threshold CC score of 0, and 92% for scores <80 (p < 0.001). Overall accuracy for determining the etiology of cardiomyopathy (differentiating ischemic from nonischemic) was 92% for this technique. CONCLUSIONS: This prospective, blinded study indicates that EBCT detected CC accurately and can noninvasively distinguish between cardiomyopathy because of CAD and nonischemic causes of left ventricular dysfunction.

Exercise testing and electron beam computed tomography in the evaluation of coronary artery disease.

OBJECTIVES: This study compared coronary artery calcium (CC) as detected by electron beam computed tomography (EBCT) with conventional stress testing in the evaluation of patients with symptoms suggestive of coronary artery disease (CAD). BACKGROUND: Exercise electrocardiogram treadmill stress testing (treadmill-ECG) is limited by its requirement of a normal resting ECG and the ability of the patient to exercise adequately. The addition of myocardial imaging agents such as technetium improves the sensitivity and specificity but substantially increases the cost and prolongs the testing time. The use of EBCT provides a noninvasive and rapid method for identifying the presence and amount of CC, which has been shown to be related to atherosclerosis, and may provide additional information in combination with more traditional noninvasive testing methods. METHODS: A total of 97 patients underwent technetium stress testing (technetium-stress), treadmill-ECG, and EBCT coronary scanning within three months of coronary angiography for the evaluation of chest pain. RESULTS: The relative risk (RR) of obstructive angiographic CAD for an abnormal test was higher for EBCT (4.53) than either treadmill-ECG (1.72) or technetium-stress (1.96). The low specificity of EBCT (47%) was improved by the addition of treadmill-ECG (83%, p < 0.05). CONCLUSIONS: Electron beam computed tomography has a higher diagnostic ability than either treadmill-ECG or technetium-stress for the detection of obstructive angiographic CAD. Electron beam computed tomography is an accurate and noninvasive alternative to traditional stress testing for the detection of obstructive CAD in symptomatic patients.

Sensitivity and specificity of assessing coronary bypass graft patency with ultrafast computed tomography: results of a multicenter study.

Because a significant number of all patients seen by cardiologists have had coronary bypass surgery, a relatively noninvasive method of assessing coronary bypass graft patency would be very helpful. Ultrafast computed tomography, by virtue of its rapid data acquisition time and reasonable spatial resolution, may be useful in this regard. To determine the sensitivity, specificity and predictive accuracy of this imaging modality as compared with cardiac catheterization, a multicenter study was undertaken. There were two parts to the study. Part I involved the evaluation of 179 grafts in 74 patients studied in the five participating centers between March 1985 and August 1986. Twenty-nine percent of these graft studies were found to be technically inadequate and were excluded before patency determinations began. The remaining group of 127 bypass grafts in 62 patients had studies adequate for interpretation. Fifty-one grafts were to the left anterior descending coronary artery or a diagonal branch, 37 to branches of the left circumflex artery and 28 to the right coronary artery or a posterior descending vessel; in addition, there were 11 internal mammary artery bypass grafts primarily into the left anterior descending or diagonal artery distribution. The sensitivity of detecting angiographically open grafts was 93.4%, the specificity of detecting angiographically closed grafts 88.9% and the predictive accuracy was 92.1%. A subsequent study (Part 2) was performed 9 months later to assess the ability to carry out technically adequate examinations. Of the 138 consecutive graft examinations (50 patients) included in this part of the study, 94.2% of the examinations were found to be technically adequate.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnostic test use in different practice settings. A controlled comparison.

Health maintenance organizations (HMOs) have lower than average medical care costs, but the reasons remain controversial. The diagnostic practices of cardiologists from an HMO, a university, and a community were therefore surveyed. First, cardiologists defined indications for coronary bypass surgery and then evaluated randomly selected case summaries of patients with chest pain. After review, the cardiologist rated the need for an exercise thallium scintiscan and for a coronary angiogram in each case. Community cardiologists had the broadest indications for bypass surgery. The HMO cardiologists chose thallium scintigraphy significantly less often than the other two types of cardiologists did. The HMO and university cardiologists both rated the need for coronary angiography significantly lower than did community cardiologists. Physicians in different practice settings therefore recommend costly diagnostic and therapeutic methods differently, even for identical patients.

Long-term outpatient vasodilator therapy of congestive heart failure. Consideration of agents at rest and during exercise.

Increased left ventricular filling pressure and reduced cardiac output are two major hemodynamic deficits in pump failure. In patients with chronic heart failure, consequences of these hemodynamic deficits and diminished cardiac reserve are manifested initially during stress and eventually at rest. The purpose of therapeutic interventions include reduction of ventricular filling pressure increase in cardiac output and improvement in cardiac reserve. To achieve these goals, the hemodynamic effects of predominantly venodilators (nitrates), predominantly arteriolar dilators (hydralazine) and the combination of nitrates and hydralazine were evaluated in patients with chronic heart failure at rest: left ventricular filling pressure (mm Hg) control 28, nitrates 17, hydralazine 25, nitrates plus hydralazine 18; cardiac output (liters/min/m2) control 2.1, nitrates 2.1, hydralazine 3.2, nitrates plus hydralazine 3.3; mean blood pressure (mm Hg) control 87, nitrates 85, hydralazine 83, nitrates plus hydralazine 85. These data suggest improved left ventricular performance with a combination of nitrates and hydralazine. Exercise hemodynamics improved in some patients, suggesting that such vasodilator therapy may be beneficial in chronic heart failure.

Beyond perfusion with ultrafast computed tomography.

Ultrafast computed tomography (CT) has been available for the clinician for nearly 10 years. Although cost, as well as availability of competing technologies, have limited its application, several investigative groups have demonstrated the feasibility of measuring regional myocardial blood flow by this method. Ultrafast CT provides accurate measurements when myocardial blood flow is normal or reduced. However, when flow is increased (e.g., by pharmacologic vasodilation), the technique underestimates flow. (This can apparently be corrected by using a complex curve-fitting technique.) Direct injection of contrast medium into the aorta distinguishes differences in endocardial and epicardial blood flow. Although imaging of myocardial perfusion has proven clinical value, there is a need for new noninvasive approaches for detecting silent coronary atherosclerosis before coronary events occur. Here it is possible to make use of the close association between coronary atherosclerosis and coronary intimal calcium, recognized over 35 years ago. Even though the amount of coronary calcium is a function of age, individuals with coronary artery disease usually have greater amounts, and the greater the number of coronary vessels with calcium, the greater the likelihood of obstructive coronary disease. Ultrafast CT has proven value for visualizing coronary calcium. No contrast medium is required and radiation exposure is approximately 425 mrads.