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Biomedical subjects

L W Klein

Publications and source records attributed to L W Klein.

At least 73 records · Page 4Linked to original sources
PubMed1987

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.

Adult↗
PubMed1987

Assessment of coronary artery stenoses by digital subtraction angiography: a pathoanatomic validation.

Automated computer assessment of coronary stenoses from digital subtraction angiographic images comparing geometric and videodensitometric algorithms was performed. Digital subtraction angiograms were acquired on a 512 X 512 X 8 bit pixel matrix at 8 frames/second. Fifteen segments from nine human cadaver coronary arteries, with lesions ranging from 0% to 97%, were analyzed. Hand injections of radiopaque dye were made during the pulsatile infusion of saline solution at physiologic pressures and flows. Individual frames best demonstrating a lesion were digitally magnified and the stenosis was measured; the operator identified only the segment of interest. The artery was then injected with a rapidly hardening gel during the same rate of infusion as that used during image acquisition. Histologic sections were cut at 2 mm intervals after fixation and elastic stains applied. Photographs of the section comparable to the site determined from the angiogram were taken, and hand planimetry by a blinded investigator was performed. There was an excellent correlation between histopathology and videodensitometry (r = 0.93; p less than 0.0001). The two geometric algorithms studied also had very good correlations (r = 0.90 and 0.84) with pathology. Two experienced angiographers, despite excellent agreement with each other, had lower correlations with pathology than any of the three computer algorithms studied (r = 0.79 and 0.83, respectively), although this difference did not attain statistical significance. This in vitro model simulating in vivo conditions validates the use of automated videodensitometric and geometric computer algorithms to interpret coronary angiography and assess severity of stenosis.

Algorithms↗
PubMed1987

Improved survival with coronary bypass surgery in patients with three-vessel coronary disease and abnormal left ventricular function. Matched case-control study in patients with potentially operable disease.

Recent studies have suggested that patients with three-vessel coronary disease and abnormal left ventricular function have better survival rates with bypass surgery than with medical therapy alone. Case-control studies may give accurate survival estimates, but to be valid, selection biases must be taken into account. A matched case-control method was used to compare survival patterns in patients treated medically or surgically during the 1980s. Fifty medical patients with potentially operable coronary disease and 46 surgical patients were matched for significant three-vessel disease and abnormal ventricular function. These two groups had no significant differences with regard to 24 variables, including age (64 +/- 8 versus 63 +/- 10 years), chest pain class, congestive heart failure signs, ejection fraction (36 +/- 8 versus 37 +/- 9 percent), segmental wall score, or a coronary score evaluating lesion site and severity. There were slight differences between the two groups with regard to congestive heart failure symptoms (p = 0.04). Patients undergoing bypass surgery had improved four-year survival rates compared with the medical group (89 versus 55 percent; p = 0.01). Thus, this study used an effective case-control method to suggest that, in the 1980s, coronary surgery improves prognosis substantially in surgically approachable patients with severe coronary disease and ventricular dysfunction.

Aged↗
PubMed1987

Absence of coronary vascular reserve in myocardium distal to a fixed coronary stenosis.

In a study to test the hypothesis that vascular reserve is exhausted in the setting of a resting blood flow deficit, the left anterior descending or circumflex artery was cannulated and perfused from the left carotid artery. After reactive hyperaemia had been assessed a stenosis was produced with a screw clamp. In the first experiment a moderate stenosis (diastolic perfusion pressure 40 mmHg) was produced in the left anterior descending artery (three dogs) or left circumflex artery (three dogs). Blood pressure was held constant with aortic constriction during intracoronary adenosine infusion (6 mumol.min-1). The stenosis was then adjusted to the preadenosine perfusion pressure. In the second experiment the anterior interventricular coronary vein was also isolated and segment length crystals were placed in the ischaemic and non-ischaemic zones. Severe stenosis (flow reduction of at least 50% and evidence of decreased segmental shortening) was produced in the cannulated left anterior descending artery (eight dogs). Intracoronary adenosine was given with aortic pressure held constant by transfusion and coronary venous drainage. In the first experiment resting coronary flow (ml.min-1) decreased from 41(3) to 29(6) (p less than 0.05) with stenosis. Coronary flow increased from 29(6) to 34(7) (p less than 0.05) with adenosine and to 50(10) (p less than 0.05) with stenosis adjustment. Subendocardial flow (ml.g-1.min-1) decreased from 0.89(0.26) to 0.78(0.23) (p less than 0.05) with adenosine and then increased from 0.94(0.49) with perfusion pressure adjustment. Subepicardial flow tended to increase with adenosine, and increased further with stenosis adjustment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1986

Medical and surgical survival in coronary artery disease in the 1980s.

The survival of 1,657 patients with angiographically proved coronary artery disease (CAD) was studied for 4 years (mean 2.0 +/- 1.2) during the 1980s to examine the prognostic importance of multiple clinical variables. One hundred of the 1,049 medically treated patients (9.5%) and 31 of the 608 surgically treated patients (5.1%) died. Multivariate analyses revealed that the strongest prognostic variables for survival in the medical group were indexes of left ventricular function (p less than 0.0001), severity of coronary stenoses (p less than 0.0001) and age (p = 0.005). However, only age (p less than 0.0001) was a significant prognostic variable in the surgically treated group. This study emphasizes the lack of prognostic significance of left ventricular function indexes and severity of coronary stenoses in surgically treated patients with CAD. These results continue the trend toward improved surgical survival shown in recent years.

Age Factors↗
PubMed1986

Videodensitometric quantitation of aortic regurgitation by digital subtraction aortography using a computer-based method analyzing time-density curves.

To assess the clinical role of computer analysis of time-density curves in the evaluation of aortic regurgitation (AR), digital subtraction aortography (DSA) and cineaortography were performed sequentially in 17 patients with varying degrees of AR (1+ to 4+) and in 4 control patients. DSA was performed at a rate of 30 frames/s on a 512 X 512 X 8 bit pixel matrix using the same total volume and injection rate, but with half the amount of contrast agent as standard cineaortography. A 30 X 30 pixel area of interest was identified in the aorta above the valve plane and in the left ventricle where the AR stream was seen. The density of both areas of interest and the ratio of left ventricular/aortic area of interest density was calculated in each frame and then plotted vs time. The ratio at the end of injection (LVd/Aod) had an excellent correlation with cineaortography (chi 2 = 19, p less than 0.001), ranging from 0 to 0.2 in patients with no AR, 0.2 to 0.5 in those with 1+ AR, 0.5 to 0.7 in those with 2+ AR, 0.7 to 0.9 in those with 3+ AR and more than 0.9 in those with 4+ AR. Thus, quantitative assessment of AR by computer analysis of time-density curves derived from DSA is a new and objective technique with significant clinical potential.

Aortic Valve Insufficiency↗
PubMed1986

Multistage analysis of exercise radionuclide angiography in coronary artery disease.

The hypothesis that serial assessment of left ventricular function during exercise radionuclide angiography provides improved diagnostic criteria for coronary artery disease (CAD) was examined. Fifty-eight consecutive patients without previous myocardial infarction were prospectively scheduled for cardiac catheterization and multistage radionuclide angiographic exercise studies. Forty-one patients had significant CAD. The traditional criterion--failure to achieve a 5% increment in ejection fraction (EF) during exercise compared with the value at rest--had 85% sensitivity but only 41% specificity for CAD. In 12 patients, EF increased early in exercise by at least 4% and then decreased a mean of 7.5%, often with worsening regional wall motion. This "up-down" EF pattern was applied as a diagnostic test in the overall study group. Analysis of changes in EF from the maximal value achieved to that at the end of exercise resulted in criteria with greater sensitivity (p less than 0.0001) for CAD than analysis of changes from rest, with similar specificity. Regional wall motion abnormalities occurring during the first exercise stage resulted in 94% specificity for CAD (p = 0.05 vs end-stage analysis), although sensitivity was low. Analyzing the maximal EF during exercise results in improved sensitivity, while analyzing the early onset of regional dysfunction results in high specificity for CAD.

Adult↗
PubMed1986

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.

Coronary Disease↗
PubMed1986

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.

Adult↗
PubMed1986

A new catheter design for use in patients with critical aortic stenosis.

A new catheter that facilitates catheterization in patients with severe aortic stenosis is described. The catheter design is capable of high-pressure injections for left ventriculography, but it maintains maneuverability and has an end hole for use with a guide wire in traversing tightly stenotic valves. Experience with this catheter in 23 patients confirmed that good-quality ventriculograms are obtained after left ventricular entry. Twenty-two of 23 patients with aortic stenosis were studied entirely with this catheter; in only one case were attempts to cross the valve unsuccessful, both with this and other catheters. In conclusion, this new catheter is recommended for routine use in patients with suspected severe aortic stenosis.

Adult↗
PubMed1986

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)

Animals↗
PubMed1986

Analysis of systolic bulging. Mechanical characteristics of acutely ischemic myocardium in the conscious dog.

To determine the mechanical factors affecting regional segmental motion after acute coronary occlusion, we studied seven conscious dogs, instrumented with sonomicrometers. Loading conditions were changed by the withdrawal of 500 ml of blood and the transfusion of 800 ml of blood. To express segmental motion, percent systolic shortening, percent systolic elongation, and early diastolic shortening were calculated. Blood withdrawal decreased left ventricular preload, increased percent systolic elongation (from 6.9 +/- 3.1% to 9.9 +/- 3.5%) and early diastolic shortening (12.9 +/- 5.3% to 16.6 +/- 5.3%), and decreased percent systolic shortening. Blood transfusion increased left ventricular preload, decreased percent systolic elongation (to 5.2 +/- 1.8%) and early diastolic shortening (8.8 +/- 2.9%), and increased percent systolic shortening. Manipulation of loading did not change regional myocardial blood flow. In acutely ischemic myocardium, the tension-length loop showed an exponential upstroke during isovolumic systole and a nearly superimposed exponential downstroke during the isovolumic relaxation phase after systole, compatible with essentially passive movement as seen with an elastic material. The changes in loading conditions affected the tension-length curve to a very minor extent. The uniformity of the curve and its exponential shape explain the load-dependency of systolic bulging and segmental motion. It is concluded that systolic bulging depends on the change in the preload tension due to the compliant portion of tension-length curve, and that shortening of ischemic myocardium during the isovolumic relaxation phase is a completely passive phenomenon.

Animals↗
PubMed1985

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.

Adult↗