Mechanisms of A-V Block

Determination of the varieties of A-V block is predicated on the precise identification of the site(s) of conduction delay as prognosis, and therapy must follow on this basis. Further electrophysiologic and pharmacologic studies will undoubtedly reveal other mechanisms on the nature of A-V transmission

Malignant anomalous right coronary artery detected by multidetector row computed tomography coronary angiography

We report a case of an anomalous origin of a right coronary artery from the left coronary sinus with an inter-arterial course, between the aorta and the main pulmonary artery. This variant has been called malignant because of its association with sudden death, especially in young asymptomatic athletes. Although these variants are rare, knowledge of cross sectional anatomy of the coronary arteries and their variants is critical, especially because some variants are associated with sudden death

Anomalous Right Coronary Artery From the Left Coronary Sinus With an Interarterial Course: Is It Really Dangerous?

Anomalous origin of the right or left coronary artery from the contralateral sinus of Valsalva is often asymptomatic, but many patients, particularly young ones, present with sudden death or myocardial ischemia without symptoms. The mechanism of sudden death in this entity is unclear and has not been fully evaluated. These anomalies are rare, and many cardiologists and radiologists are unfamiliar with them. Surgical repair is recommended, especially with anomalous origin of the left coronary artery (LCA). However, there is controversy concerning the treatment of anomalous right coronary artery (RCA) with interarterial course due to its relatively high incidence and the fact that it leads to few, if any, clinical problems

ORIGINAL ARTICLES Assessment of Jeopardized Myocardium in Patients with One-vessel Disease

SUMMARY The size of the perfusion defect was assessed from a quantitative analysis of exercise thallium-201 images. Quantitative analysis was determined by measuring the area and the perimeter of the perfusion defect and expressing it as a percentage of the total left ventricular area or perimeter in three projections. Using this technique, we studied 50 patients with one-vessel disease of 50% or greater diameter narrowing. The planimetric and the perimetric methods correlated well (p < 0.001, r = 0.97). Of the 11 patients with less than 70% diameter narrowing, only one patient had abnormal exercise thallium-201 images. Of the remaining 39 patients with 70% or greater diameter narrowing, 35 circumflex disease. Mortality rates undoubtedly depend on left ventricular function: The worse the function, the poorer the prognosis. Therefore, the extent of jeopardized myocardium may have prognostic importance in patients with one-vessel disease; patients with more jeopardized myocardium may be at a higher risk of developing severe left ventricular dysfunction in the event of myocardium infarction. The purpose of this study was to assess the extent of jeopardized myocardium in patients with one-vessel disease by using quantitative analysis of exercise images, a simple technique that does not require computer manipulation, and to define the factors that affect the size of the defects in these patients. Materials and Methods We reviewed our records of exercise thallium-201 imaging and identified 50 patients with one-vessel disease who had undergone exercise perfusion imaging within 3 months of coronary angiography. There were 46 men and four women, ages 32-63 years (mean 52 years). Patients with associated cardiac diseases such as valvular heart disease or idiopathic hypertrophic subaortic stenosis and patients who had had previous bypass surgery were excluded. All patients were evaluated for symptoms of angina pectoris. No patient had unstable angina or historic or electrocardiographic evidence of myocardial infarction. Left-and right-heart catheterization, left ventriculography and coronary arteriography were per- formed with standard techniques. Each coronary vessel was visualized in multiple projections, including the sagittal oblique projection. Each patient had at least 50% diameter narrowing of one coronary artery. The lesion in the left anterior descending artery was classified as either proximal or distal to the first septal perforator and diagonal branches. In each patient with left circumflex artery disease, the lesion was before or involved the major posterolateral branch. In each patient with right coronary artery disease, the lesion was before the crux. The coronary circulation was rightdominant in patients with left circumflex or right coronary artery disease. The remaining vessels were either free of disease or had only slight luminal irregularities. Collaterals were considered present and significant if the collateral flow partially or completely opacified the diseased vessel beyond the site of occlusion or narrowing. The left ventriculograms, which were assessed qualitatively for wall-motion abnormalities, showed that none of these patients had akinetic or dyskinetic segments. The angiograms were reviewed by two experienced angiographers, and the consensus of both reviewers was used in the final interpretation. Exercise treadmill testing was performed according to the Bruce protocol. The end points of exercise were 2 2 mm of horizontal or downsloping ST depression (with or without angina), excessive fatigue or leg weakness, hypotension, frequent ventricular premature complexes, or attainment of at least 85% of the predicted maximal heart rate. Three electrocardiographic leads (V1, V, and aVF) were continuously monitored; lead V5 was used for interpretation. Blood pressure was obtained by the cuff method every 2 minutes. At peak exercise, 2 mCi of thallium-201 were injected intravenously and flushed with dextrose and water. The patient continued to exercise for 1 more minute. Within 10 minutes after injection, images were obtained in the anterior, left anterior oblique and left lateral projections by means of a commercially available scintillation camera (Baird Atomic System-77) equipped with a high-resolution, parallel-hole, 11/2-inch-thick collimator. Redistribution images were obtained 4 hours after exercise in the projections that showed the perfusion abnormalities. All patients in the study with initial abnormal images showed partia'L or complete redistribution in the delayed images. Our method for obtaining the exercise thallium-201 scintigrams has been described." 6 8 21-24 In brief, images were accumulated for a preset count (750,000 to 1,250,000 total counts), which required 8-12 minutes per projection. All images were corrected for background and for detector nonuniformity. Images were displayed on a television screen on a scale of 16 gray shades or 16 colors. The highest count displayed represents 100% on the scale and all other counts are digitally normalized to the maximum. Each of the 16 shades or colors represents a 6.25% increment in counts within the image. Depending on the visual in--spection of the background contribution, 20-30% background subtraction is used and the 16 colors are displayed over the remaining count range. In addition, the images were processed using an algorithm that weighs and spatially averages five adjacent data points in the matrix. The net result is a color-coded isocount contour display of the myocardial thallium-201 distribution. Polaroid pictures were obtained of the computer-smoothed images. We and others7' 25 have found that the color-coded display of the images improve the interpretation. Segments of the myocardium showing 25% decrease in counts (four-color shift) are considered abnormal. The borders of the defects are outlined by two independent observers and minor disagreements were settled by arbitration between the two observers. Quantitative analysis was done by two methods. In the first method, the size of the thallium-201 defect was determined by the method of Niess et al.26 with a computerized planimetry system (Hewlett-Packard 982A calculator and digitizer). This method expresses the size of thallium-201 perfusion defects as a percentage of total potential thallium uptake. The size of the defect was computed in each projection and expressed as a percentage of the total area of the myocardium, excluding the left ventricular cavity and the region of the valves. The average of the three projections was also determined ( In the second method, the perimeter of the defect was measured and expressed as a percentage of the total left ventricular perimeter in each projection ( Statistical analysis was performed using the t test or the analysis of variance when appropriate