Detection of coronary artery calcium to differentiate patients with early coronary atherosclerosis from luminally normal arteries.

Patients with angiographic evidence of early coronary atherosclerosis (<50% diameter stenosis) have a poorer prognosis than those with normal arteries and may benefit from more aggressive interventions targeted toward the primary prevention of cardiovascular disease. Using a calcium score of 5, fast computed tomography was able to identify 59% of patients with early atherosclerosis, while excluding 87% of patients with smooth, luminally normal coronary arteries.

Fast computed tomography detection of coronary calcification in the diagnosis of coronary artery disease. Comparison with angiography in patients < 50 years old.

BACKGROUND: The predominant cause of coronary artery calcification is atherosclerosis. Although fast x-ray computed tomography (CT) has been demonstrated to be a sensitive technique to detect coronary calcification, the increasing prevalence of calcification with age has been associated with a low specificity for identifying obstructive atherosclerosis. We hypothesized that the specificity of this test would be improved in a younger patient population, making it more useful in the diagnosis of coronary artery disease. METHODS AND RESULTS: We compared fast CT-detected calcification with coronary angiography in 106 patients under the age of 50 years. Nonenhanced fast CT scans consisting of 20 contiguous 3-mm tomograms of the proximal coronary arteries were obtained during a single breath hold. A positive scan was defined as 4 contiguous voxels (> or = 1 mm2) of density > 130 Hounsfield units in the region of the epicardial coronary arteries. Calcification detected by fast CT had an 85% sensitivity to predict patients with significant coronary artery disease (> or = 50% diameter stenosis), with a specificity of 45%. Although the sensitivity to detect multivessel disease was 94%, the sensitivity to detect single-vessel disease was 75%. Changing the threshold for defining a positive fast CT scan from 4 to 2 contiguous voxels produced a small improvement in sensitivity, to 88%, but reduced specificity to 36%. CONCLUSIONS: Although the specificity to detect angiographically significant coronary disease with fast CT improves in a younger patient population, it continues to be relatively low. In contrast to older patient populations, a small but significant number of patients < 50 years old with angiographically significant coronary artery disease do not have coronary calcification demonstrated by fast CT. Thus, caution should be used in excluding significant coronary artery disease on the basis of a negative fast CT study.

Effectiveness of the Arani double-loop guiding catheters in angioplasty of aorto-coronary vein grafts.

Double-loop guiding catheters have been used for angioplasty of aorto-coronary vein grafts (VG) or grafted arteries through the VG in 31 cases. A catheter with a 90 degrees primary curve was usually the best choice for angioplasty of the VG to the right coronary artery (RCA). For angioplasty of the VG to the left coronary artery branches (LCA), a 90 degrees primary curve was used when the proximal segment of the VG was oriented horizontally and a 75 degrees (USCI, C.R. Bard, Inc., Billerica, MA) was used when the proximal segment was directed superiorly. Angioplasty of 32 lesions was attempted in 31 patients. These catheters provided good "back-up" in angioplasty of 30 lesions (94%). The lesions were crossed with balloon catheters in 29 cases (91%). There was one acute VG occlusion requiring coronary artery bypass graft (CABG) surgery, a complication not attributed to the guiding catheter. We conclude that Arani guiding catheters provide strong back-up, are helpful in angioplasty of the vein grafts, and could be used as the primary choice for VG angioplasties.

Double loop guiding catheter: a primary catheter for angioplasty of the right coronary artery.

Double loop guiding catheters have been used for percutaneous transluminal coronary angioplasty (PTCA) of the right coronary artery (RCA) in 42 consecutive cases. A catheter with a 90-degree primary curve was used when the proximal RCA had horizontal or inferior orientation. When the proximal segment of the RCA was oriented superiorly (shepherd's crook), the catheter with a 75-degree primary curve was used. Catheters were fabricated with short (1.5 cm) or long (2.3 cm) (USCI, C.R. Bard, Inc., Billerica, MA) distal tips. Short-tip catheters were satisfactory in the majority of cases. When the RCA had a complex course and more backup was necessary or when the ascending aorta was wide, long-tip catheters were found to be the best choice. Angioplasty of 49 lesions was attempted in 42 consecutive patients. In 39 patients successful dilatation was achieved (93%). In three patients the procedure was unsuccessful. In one patient, the lesion could not be crossed with the guidewire despite an excellent backup. In another patient, two of three stenoses were dilated successfully; the distal lesion was crossed with a guidewire but could not be crossed with the balloon catheter in spite of a good backup. The lack of a satisfactory engagement and inadequate backup were responsible for the failure in only one patient. There were no complications related to these guiding catheters. We conclude that double loop guiding catheters are safe and can be the primary choice in all right coronary angioplasties. These catheters provide an excellent backup with consequent high success rate.

Reductions in coronary flow under resting conditions in collateral-dependent myocardium of patients with complete occlusion of the left anterior descending coronary artery.

Flow per unit weight in collateral-dependent myocardium was quantified selectively in seven patients with complete occlusion of the proximal left anterior descending artery and prominent distal collateralization from the right coronary artery by infusing dissolved hydrogen into the right coronary artery for 10 to 15 minutes and monitoring hydrogen desaturation in the great cardiac vein. Coronary flow per unit weight in all myocardium draining into the great cardiac vein was quantified simultaneously by having the patient breathe helium and by monitoring arterial and great cardiac vein helium desaturation. Flow per unit weight in collateral-dependent myocardium averaged 38 +/- 8 (standard deviation) ml/min per 100 g and was in each case below the 95% confidence limit for normal individuals with the same rate-pressure product. Flow per unit weight in all myocardium draining into the great cardiac vein was systematically higher (51 +/- 8 ml/min per 100 g); because arteries other than the anterior descending had no stenoses greater than 30% in diameter, these values presumably reflect mixtures of subnormally perfused collateralized myocardium and adjacent normally perfused tissue. The findings suggest that coronary flow per unit weight is not maintained at usual basal values in densely collaterlized myocardium that is entirely collateral-dependent. The reductions in flow are presumably associated with marked reductions in local arterial pressure and raise the possibility of a chronic reduction in local myocardial metabolic demand.

Long-term survival after coronary bypass surgery. Comparison of various subsets of patients with general population.

Life-table analysis consecutive cases of isolated coronary bypass surgery at the Buffalo Hospital between 1973 and 1977 showed an estimated survival of 94 per cent at five years, equal to that of an age- and sex-matched group of the US population. Subsets of these patients divided according to sex, age, number of vessels narrowed, number of segments grafted, history of myocardial infarction, ejection fraction, and presence of unstable angina have estimated survivals not statistically less in any of these subsets than that of matched cohorts of the general population.

Lordotic right posterior oblique projection of the left coronary artery: a speical view for special anatomy.

The lordotic right posterior oblique projection of the left coronary artery is obtained by combining cranial angulation of the X-ray beam with rotation of the patient into the right posterior oblique position. This projection is helpful for separation of the main left coronary artery and the proximal portions of the left anterior descending and circumflex divisions, especially in patients in whom the left anterior descending artery is directed cephalad early in its course. The obtaining of an image from the lordotic right posterior oblique projection adds less than two minutes to the procedure and improves arteriographic assessment of the left coronary artery.

Evaluation of venous bypass grafts from aorta to coronary artery by inert gas desaturation and direct flowmeter techniques.

Blood flow through aorta-to-coronary artery bypass grafts has been measured selectively in 16 patients at or within 6 wk after operation. Inert gas desaturation curves were obtained from coronary venous blood samples after a 7-15 min infusion of dissolved H(2) directly into the graft. Samples were analyzed chromatographically and curves resolved to 1-3% of initial H(2) concentrations. Average flow per unit volume (F/V) was 67+/-21 (sd) ml/min per 100 g. Semilogarithmic plots showed F/V to be distributed heterogeneously in every case. In nine studies at operation, H(2) measurements of average F/V were combined with electromagnetic measurements of total flow to estimate revascularized tissue mass. Electromagnetic flows ranged from 25 to 170 ml/min and averaged 69 ml/min. Tissue mass ranged from 46 to 155 g and averaged 88 g. We conclude that bypass grafts provide nutritive flow to significant amounts of myocardium at and shortly after operation. However, nutritive flow is not distributed evenly throughout the revascularized segment. The majority of the segment has a F/V within the accepted range of normal but there remain areas in which F/V is reduced significantly. The combination of inert gas and electromagnetic techniques allows a revascularized area to be characterized in terms of total flow, F/V, and tissue mass.

Measurement of cardiac output in man with a nonrecirculating indicator.

The present investigation was undertaken to evaluate the utility of constant-rate injection of a nonrecirculating indicator (H(2)) for the measurement of cardiac output in man. 42 patients were studied during cardiac catheterization and 8 during acute complications of arteriosclerotic heart disease, including acute myocardial infarction. Pulmonary (or systemic) arterial H(2) concentration was measured chromatographically from 2.0 ml blood samples drawn during constant-rate injection of dissolved H(2) into the systemic venous circulation (or left heart). The chromatograph was a thermal conductivity unit housed in a constant-temperature water bath to achieve an improved signal-to-noise ratio. Intrapulmonary H(2) elimination from mixed venous blood was measured directly in 14 patients and averaged 98 +/-1.5% (SD). Reproducibility of output measurements was evaluated using triplicate determinations obtained over 45-60 sec in 25 consecutive patients. Coefficients of variation (SD/Mean x 100) averaged 3.4 +/-2.0%, making it possible to evaluate relatively small changes in measured output with conventional statistical tests. Individual measurements could be repeated at 10-15 sec intervals. Comparisons of H(2) and direct Fick measurements were made in 14 patients; H(2) outputs averaged 106 +/-4% (SEM) of Fick outputs (P > 0.1). Comparisons of H(2) and dye dilution measurements were performed in an additional 24 patients. Seven had angiographically-negligible valvular regurgitation and dye outputs averaged 106 +/-3% of H(2) outputs (P > 0.1). 17 had moderate-to-severe regurigation and dye outputs averaged 91 +/-4% of H(2) outputs (P < 0.05), suggesting a small but systematic error due to undetected recirculation of dye. The H(2) technique appears advantageous for rapidly repeated determinations of output, for quantitation of small changes in output, and for situations in which recirculation of conventional indicators is a potentially significant problem.