Jai B. Agarwal

Prognostic significance of severe narrowing of the proximal portion of the left anterior descending coronary artery

To determine the prognostic importance of significant narrowings involving the proximal left anterior descending coronary artery (LAD), 866 medically treated patients with significant coronary artery disease (CAD) were followed after cardiac catheterization for a mean of 17 months (range 1 to 46). Coronary narrowings in all patients were evaluated based on site relative to large branches and on angiographic severity. Prognosis was best predicted by the presence of at least 70% diameter reductions in the LAD before the first 2 large branches (chi 2 = 16, p = 0.0001). At 3 years, there was a 94% cumulative survival rate in patients with less than 70% stenoses at this location, but an 82% survival rate in patients with 70% or more stenoses (p less than 0.0001). In addition, although the presence of proximal LAD narrowings was the best predictor of prognosis in patients with a low global ejection fraction, this was not so in patients with normal ejection fractions, as this subgroup had an excellent overall prognosis. Thus, the presence and severity of significant stenoses in the proximal LAD are stronger predictors of prognosis than stenoses elsewhere in the major coronary arteries. The presence of an angiographically significant narrowing in this anatomic location is highly correlated with an increased 1- to 3-year mortality rate.

Magnetic resonance imaging to evaluate patency of aortocoronary bypass grafts.

To assess the efficacy of magnetic resonance (MR) imaging in evaluating graft patency after coronary bypass surgery, 20 patients who had prior surgery (average 5.5 years, range 1.5 to 14) and recent cardiac catheterization because of chest pain were studied. No patient had surgical intervention or change in symptoms in the time interval between catheterization and MR imaging. These 20 patients had a total of 47 grafts, defined as proximal anastomoses: 20 to the left anterior descending or diagonal artery (LAD), 13 to the left circumflex artery marginal branches (LCX), and 14 to the right coronary artery or posterior descending artery (RCA). The patients underwent cardiac and respiratory gated MR scans in a 0.5 tesla magnet with an echo time of 22 msec and two repetitions in a 128 X 256 matrix. In-plane resolution was 2.7 mm. Every patient had a scan in the transaxial plane and some underwent scanning in the sagittal and coronal planes as well. A graft was considered patent by MR when a signal-free lumen was visualized in an anatomic position consistent with that of a bypass graft, had a lumen larger than the native vessels, was seen on more than one slice, and was seen at a level higher than that of the native vessels. If a known graft was not seen it was considered occluded. The scans were interpreted by consensus of two physicians aware of the operative but not the cardiac catheterization data.(ABSTRACT TRUNCATED AT 250 WORDS)

Heart rate variability for risk stratification of life-threatening arrhythmias

[The following is a position statement prepared by the Cardiovascular Technology Assessment Committee: LEONARD S. DREIFUS, MD, FACC, Chairman, JAI B. AGARWAL, MBBS, FACC, ELIAS H. BOTVINICK, MD, FACC, KEITH C. FERDINAND, MD, FACC, CHARLES FISCH, MD, FACC, ex officio, JOHN D. FISHER, MD, FACC, J. WARD KENNEDY, MD, FACC, ex officio, RICHARD E. KERBER, MD, FACC, CHARLES R. LAMBERT, MD, FACC, OKIKE N. OKIKE, MD, FACC, ERIC N. PRYSTOWSKY, MD, FACC, SANJEEV V. SAKSENA, MBBS, FACC, JOHN S. SCHROEDER, MD, FACC, ex officio, DAVID O. WILLIAMS, MD, FACC. This position statement was approved by the Board of Trustees of the American College of Cardiology on March 13, 1993. Reprints are available from: Educational Products Sales and Marketing; 9111 Old Georgetown Road; Bethesda, MD 20814; 800/257-4740.]

Prognosis of symptomatic coronary artery disease in young adults aged 40 years or less

The clinical course and coronary angiographic features of symptomatic coronary artery disease (CAD) in patients younger than 40 years old are described with particular emphasis on the prevalence of myocardial infarction and the degree of diminished functional capacity. Eighty-five patients with CAD proven by coronary angiography were studied. There were 73 men and 12 women aged 27 to 40 years. Fifty-nine patients presented with acute myocardial infarction, most of whom denied previous chest pain, and 14% (12 patients) presented with less acute chest pain syndromes. Coronary angiography was performed in all patients, and greater than or equal to 70% luminal diameter narrowing was considered significant. Coronary angiographic findings reveal 51% with 1-vessel CAD, 31% with 2-vessel and 19% with 3-vessel. Subsequently, 23 patients had coronary artery bypass graft surgery, 7 underwent angioplasty and 55 were treated medically. Follow-up for a mean of 3 years revealed only 1 death and 4 subsequent hospital admissions for cardiac events. Fifty-three percent of the patients are entirely pain free, and only 4 (5%) have significant symptoms of angina pectoris. Although 15 (18%) are not employed regularly, the remainder work full- or part-time, or plan to work in the near future. These data suggest that the short-term prognosis and functional status of young patients with CAD is excellent.

Rate of left ventricular functional recovery by radionuclide angiography after exercise in coronary artery disease

To characterize determinants of the rate of recovery of left ventricular (LV) function after exercise-induced ischemia, sequential postexercise radionuclide angiography was performed prospectively in 38 consecutive patients with documented coronary artery disease (CAD). In each patient new or increased regional asynergy developed or absolute ejection fraction decreased at least 4% during exercise. Twenty patients showed immediate recovery of LV function after exercise (group 1) and 18 showed delayed recovery (group 2). Ejection fraction in the first postexercise period was significantly greater in group 1 (65 +/- 12%) than in group 2 (55 +/- 11%) (p less than 0.01). The mean number of coronary arteries with at least 70% diameter narrowing was greater in group 2 (2.7 +/- 0.5) than in group 1 (2.0 +/- 0.9) (p = 0.026); CAD score was also greater in group 2 than in group 1 (p = 0.005). The increase in LV end-diastolic volume from rest to end exercise was greater in group 2 than in group 1 (p = 0.005); neither the change in LV volume nor the change in heart rate or blood pressure after exercise separated the groups. The only independent predictor of the rate of functional recovery was the degree of exercise-induced regional myocardial asynergy (p less than 0.001). Thus, exercise radionuclide angiography in patients with CAD provides a model for evaluating postischemic myocardial function. Delayed functional recovery is associated with extensive exercise-induced regional asynergy as a result of severe CAD and is not primarily influenced by hemodynamic changes.

Effects of previous myocardial infarction on measurements of reactive hyperemia and the coronary vascular reserve

The measurement of coronary vascular reserve by the reactive hyperemic response to ischemia has been advocated as a practical method of assessing the physiologic significance of coronary stenoses. Because the concept of measuring coronary blood flow during maximal vasodilation assumes a normal arteriolar network and viable myocardium, the presence of previous myocardial infarction may cause a significant decrease in the coronary reserve unrelated to the severity of a coronary stenosis itself. To determine the potential importance of this effect, rest and hyperemic coronary blood flow were measured in 14 dogs in the regions subtended by the left anterior descending and left circumflex coronary arteries. One hour occlusion of the left anterior descending artery followed by reperfusion was performed in 10 dogs; the 4 remaining dogs in which no occlusion was performed served as control animals (group 3). One week later, rest and hyperemic blood flow measurements were repeated in all 14 dogs. Of the 10 dogs undergoing left anterior descending artery occlusion, 5 had a large infarct (group 1) and 5 had a small infarct (group 2). In group 1 in the 1 week study, both the coronary reserve in the left anterior descending artery zone and the ratio of the coronary reserve in this zone and the left circumflex artery zone decreased compared with values before occlusion (from 425 +/- 134 to 150 +/- 34% and from 1.56 +/- 0.40 to 0.68 +/- 0.31, respectively; both p = 0.007).(ABSTRACT TRUNCATED AT 250 WORDS)

Importance of total life consumption of cigarettes as a risk factor for coronary artery disease

Cigarette smoking is an established risk factor for the occurrence of cardiovascular events and mortality. Whether recent smoking history or total life consumption best represents the increased risk due to smoking has not been previously established. Thus, stepwise logistic regression analysis was used to determine the relative contributions of these factors to the risk of having significant coronary artery disease in 1,349 patients who underwent cardiac catheterization. Six risk factors were analyzed: total pack-years, current packs smoked per day, age, gender, family history and symptomatic status. The results of this analysis showed that total pack-years, but not current packs per day, is a significant independent risk factor for the development of coronary artery disease. This was true in every age group up to but not older than age 70 years. Although the overall risk was lower in younger patients and in patients with less typical symptoms of angina, the relative risk in cigarette smokers relative to pack-years was consistently greater. The risk of total life consumption of cigarettes is thus greater than has heretofore been realized, particularly in persons who would otherwise be categorized as low risk.

Interventricular septal motion: biventricular angiographic assessment of its relative contribution to left and right ventricular contraction.

The interventricular septum (IVS) has conventionally been regarded as a functional part of the left ventricle (LV). To determine its normal range of motion, simultaneous biventricular cineangiograms (60 frames/sec) were performed (600 left anterior oblique) in nine subjects without coronary or other heart disease. Arrhythmias were avoided by using a specially designed right ventricular (RV) angiographic catheter. IVS motion was studied qualitatively by three observers and quantitatively by superimposing end-systolic and diastolic frames using intra- and extracardiac reference points. Two transverse chords that trisected the endsystolic length of the IVS were drawn to quantitate IVS, LV and RV free wall motion. Qualitatively, the IVS thickened toward both RV and LV cavities as a result of shortening on its longitudinal axis. LV motion was 39.9 ± 7.2% on the transverse axis, of which 31.2 ± 5.2% was contributed by the LV free wall and 8.5 + 2.1% by IVS. RV transverse axis motion was 36.9 ± 3.7%, of which 28.6 ± 2.1% was contributed by the RV free wall and 8.3 ± 2.3% by IVS motion. There was no difference between IVS motion toward the LV and that toward the RV. The IVS longitudinal axis shortened by 17.4 ± 2.8% (p < 0.001). The mean systolic IVS thickness increased symmetrically from 7.43 ± 0.55 mm to 12.49 ± 0.39 mm (p < 0.001). In brief, the IVS thickens on its transverse axis and shortens on its longitudinal axis, contributing equally to RV and LV function.

The effects of nifedipine on myocardial blood flow and contraction during ischemia in the dog.

Nifedipine has been proposed as an agent to preserve viability and function of ischemic myocardium. We studied 23 open-chest dogs that underwent carotid-to-left anterior coronary artery perfusion with flow probe and perfusion pressure monitoring. Segment length was measured with ultrasonic crystals in the ischemic and nonischemic endocardium. Myocardial blood flow was measured with radioactive microspheres. Partial coronary occlusion was performed to 25 mm Hg diastolic perfusion pressure. Ten dogs received intracoronary nifedipine, 10 fig, and 13 dogs received i.v. nifedipine, 3, g/kg/min. Nifedipine resulted in an increase in segmental shortening in both groups, but nonischemic zone shortening did not change in either group. Nifedipine did not affect myocardial blood flow in the ischemic zone, but increased flow in the nonischemic zone in the group that received i.v. nifedipine. Thus, nifedipine appears to have a direct beneficial effect on ischemic myocardium.

Evaluation of "ischemia at a distance" : effects of coronary occlusion on a remote area of left ventricle

The effect of coronary occlusion on blood flow and function in a remote zone of the left ventricle was studied in 21 open-chest dogs. Group A consisted of 6 dogs not undergoing left circumflex (LC) coronary artery cannulation. The other 15 dogs underwent cannulation of the LC artery followed by partial occlusion to 40 mm Hg diastolic perfusion pressure. Of these dogs, 7 with constant perfusion pressure (group B) were separately evaluated from 8 with declining perfusion pressure (group C). Sequentially more proximal left anterior descending (LAD) occlusions were performed in each group. Blood flow in the LC zone remained unchanged in group A after sequential LAD occlusions, whereas in groups B and C distal and proximal LAD occlusions caused progressive reduction in LC flow. Although in group A segment shortening improved in the LC zone after distal LAD occlusion, in groups B and C progressive impairment in segmental shortening was observed in the LC zone after distal and proximal LAD occlusions. Thus, in the setting of critical coronary stenosis in a zone, total occlusion in another coronary artery can initiate a series of events leading to decreased blood flow in the territory of the stenotic coronary artery, resulting in ischemia and impaired segmental function.