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Biomedical subjects

K Cohn

Publications and source records attributed to K Cohn.

At least 37 records · Page 2Linked to original sources
PubMed1977

Heart failure. A proposed definition and classification.

Heart failure exists when either the systolic or diastolic operation of the ventricle is impaired to a degree that, despite compensatory mechanisms, the demands of the peripheral organs are not satisfied, the peripheral muscle shortens inadequately, and/or the pulmonary or systemic venous system becomes congested from high filling pressures. Since every pumping system has finite limits and can fail if excessive and prolonged demands are made on it, any definition of failure must take into consideration the degree of stress imposed and whether or not the cardiac response is appropriate or subnormal. When failure is present, it becomes essential to discern whether it involves the intrinsic pumping structures of the heart, the myocardial cells, or, rather, whether failure of one of the other components of the integrated cardiovascular system (for example, valvular dysfunction, ruptured ventricular septum) has occurred.

Adult↗
PubMed1977

Asymptomatic coronary artery disease and coronary bypass surgery.

The actuarial survival curves of "medically treated" patients whose arteriographic studies demonstrated coronary arterial lesions of various degrees-- now used widt applicable to the asymptomatic patient. No information is available regarding the course or prognosis of the asymptomatic patient with demonstrated lesions in the coronary arteries. For the reasons explained one can propose a hypothesis that the overall prognosis of this type of patient is better than average, probably better than that shown in the best data collected on symptomatic patients. The prophylactic value of aortocoronary bypass operations in preventing myocardial infarction and death has not been established. One can therefore question the justification for the wide case-finding effort of subjecting asymptomatic persons to coronary arteriography, even in light of the low risk of this procedure, unless unusual findings suggest an especially poor prognosis (one example might be past myocardial infarction in a very young patient). Although there are exceptional instances when prophylactic surgery is indicated for asymptomatic patients, further investigation of this subject is needed before the procedure becomes generally accepted.

Coronary Angiography↗
PubMed1976

Clinical syndrome of variant angina with normal coronary arteriogram.

We compared patients with variant angina (ST-segment elevation during pain) who had normal or near normal coronary arteriograms (Group 1) with 20 in whom variant angina occurred in the presence of obstructive coronary lesions (Group 2). A long history of nonexertional angina without angina of effort or previous infarction was the rule in Group 1, whereas recent-onset unstable angina preceded by effort angina and infarction predominated in Group 2 (P less than 0.001). Normal electrocardiograms at rest, with ischemic ST-segment elevation in the inferior leads, and ischemia-induced heart block and bradycardia, characterized Group 1, whereas abnormal electrocardiograms, ischemic involvement or fibrillation were more common in Group 2 (P less than 0.001). Variant angina with normal coronary arteriogram generally has a benign course and is probably unrelated to atherosclerosis.

Adult↗
PubMed1976

The "athletic heart". Prevalence and physiological significance of left ventricular enlargement in distance runners.

To evaluate the prevalence and importance of "physiological" left ventricular hypertrophy (LVH) in athletes, 30 marathon runners were studied. Electrocardiographic evidence of LVH, present in 24 subjects, was associated with concomitant echocardiographic evidence of a thickened left ventricular (LV) posterior wall in five, with an enlarged end-diastolic LV diameter in three, as well as with roentgenographic evidence of cardiomegaly in three subjects. Echocardiographic evidence of superior LV function was noted in six. Maximal treadmill stress provoked no ischemic change. Cardiac hypertrophy and dilatation commonly develop in well-conditioned athletes, but the changes in LV size are slight. This "physiological" type of LVH does not lead to an ischemic response during exercise, in contrast to that which is seen in pathological forms of LVH. Physiological LVH may, however, contribute to superior ventricular function.

Cardiomegaly↗
PubMed1976

Use of the electrocardiogram as an aid in screening for left ventricular aneurysm.

Attempting to cull from a population of patients with coronary artery disease or cardiomyopathy, a subgroup in whom left ventriculography might most reasonably be performed in search of a surgically resectable ventricular aneurysm, the electrocardiograms (ECGs) and ventriculograms of 96 patients were analyzed. This study was conceived to test the value of the ECG as an initial screening technique. Patients with normal ventricular contractile motion in the presence of coronary artery disease rarely showed ST segment elevation exceeding 2 mm in any lead, and even more rarely showed Q waves in corresponding leads. All patients with well defined left ventricular aneurysms had at least 1 mm ST segment elevation, and the majority (73%) had ST elevation of 2 mm or greater; in 80% of these, there were associated Q waves in the same lead. In patients with only local areas of hypocontractility, the frequency of ST segment elevation with concomitant Q waves was significantly less (approximately 50%) than that seen in patients with aneurysms. It is concluded that patients with suspected or proven coronary disease who fail to demonstrate ST segment elevation are unlikely to have ventricular aneurysms and, thus, would receive little diagnostic benefit from left ventriculography. The presence of ST segment elevation, with or without associated Q waves in the same leads, is a helpful screening sign, raising the possibility of a surgically remediable lesion such as a ventricular aneurysm, but similar electrocardiographic patterns are also seen in patients with non-operable localized or generalized disorders of contraction. Having discovered ST elevation, then, left ventriculography becomes a reasonable next step - when otherwise indicated - in delineating the type of contractile disorder as well as the amount of adequately functioning muscle.

Action Potentials↗
PubMed1976

Right atrial versus left atrial echo zones: a proposed new criterion for determining the atrial site of retrograde preexcitation.

In a patient whose electrocardiogram (ECG) initially (1966) showed a Type A Wolff-Parkinson-White pattern, recurrent supraventricular tachycardia (SVT) developed but never subsequently showed antegrade bypass conduction. Intracardiac pacing studies (1975) revealed that premature high right atrial (induced 250-450 msec after atrial depolarization) or coronary sinus depolarization (250-550 msec) resulted in SVT. Late coronary sinus depolarization resulted in SVT without A-H prolongation. During SVT, P wave morphology changed and the coronary sinus atrial electrogram preceded that from the low right atrium; retrograde ventriculoatrial conduction time was 240 msec. Neither pacing the high right atrium or coronary sinus up to rates of 200 beats/min nor progressive atrial premature depolarizations from the high right atrium or coronary sinus resulted in antegrade bypass conduction. Failure of antegrade bypass conduction does not preclude SVT due to retrograde preexcitation and must be distinguished from atrioventricular (A-V) nodal reentry. Atrial effective refractory period (200 msec) was shorter than the minimal time required for an atrial impulse to return to the atrium (380 msec), suggesting concealed antegrade bypass conduction. Stimulation of the atrium linked to the A-V bypass results in earlier bypass activation and recovery and explains the differing high right atrial vs coronary sinus echo zones.

Adult↗
PubMed1976

Interpretation and limitations in stress testing.

In summary, although exercise is, as is every other procedure, imperfect with regard to sensitivity and specificity, it provides an invalualbe adjunct in the evaluation of patients with coronary disease. The test is simple, inexpensive, safe and rapidly performed and is an invaluable aid in screening patients with possible coronary disease. It is used in an asymptomatic population for industrial purposes, is useful in assessing the etiology of otherwise undiagnosed chest pain, helpful in evaluating the overall severity of ischemia [and therefore in culling-out those patients that might benefit from coronary angiography], is useful in following the course of patients with proven coronary disease [including those with acute myocardial infarction], and has found a place in the follow-up evaluation of individuals having aortocoronary bypass surgery. As a screening procedure, the treadmill test aids in seeking out that group of patients with coronary disease with potentially malignant lesions, i.e. main left coronary lesions, triple-vessel disease and [to a lesser extent] severe proximal left anterior descending coronary disease. Hence, the finding of marked depth of ST depression, prolonged duration of ischemia associated with deep ST segments, serious exercise-induced ventricular arrhythmias and hypotension produced during mild-to-moderate exercise might each be an indication of extensive coronary angiography. In many cases exercise testing is superior to coronary angiography, being a simpler, safer screening procedure, and a more functional test in documenting the presence or absence of coronary insufficiency.

Aged↗
PubMed1976

Echocardiographic assessment of the level of cardiac compensation in valvular heart disease.

The level of cardiac compensation in valvular disease was studied by relating echocardiographic and cardiac catheterization measurements. Three groups -- compensated, intermediately compensated, and decompensated -- were defined according to the left ventricular angiographic pattern and cardiac output. The echocardiographic ejection indices, percent left ventricular minor diameter shortening, ejection fraction, and fiber shortening rate were significantly higher than normal in compensated mitral regurgitation, lower then normal in compensated aortic stenosis, and within normal limits in compensated aortic insufficiency. In the decomposed state these indices were depressed. Intermediate compensation was best recognized by combining several echocardiographic variables into an echocardiographic score based on multivariate discriminant function analysis. Thus, the compensated volume overload states (aortic and mitral regurgitation) and pressure overload state (aortic stenosis) have separate sets of "normal" echocardiographic values; low ejection indices characterize the decompensated group, while recognition of intermediate compensation requires analysis of multiple echocardiographic variables.

Adult↗
PubMed1976

Marked depth of ST-segment depression during treadmill exercise testing; indicator of severe coronary artery disease.

This study was designed to evaluate whether treadmill stress testing would facilitate selection of patients with advanced coronary artery disease and, specifically, whether markedly abnormal ischemic responses could be used as indicators of severity of disease. Among 59 consecutive patients with documented coronary artery disease having both maximal treadmill testing and coronary angiographic studies, 15 (group 1) had normal responses to exercise, 18 (group 2) showed 1 to 2.9 mm "ischemic" (flat or downward-sloping) ST-segment depression, and 26 (group 3) demonstrated marked (or equal to 3 mm) ischemic responses. Group 3 had statistically significant higher incidences of triple-vessel disease (18/26; 69 percent) and proximal lesions of the left anterior descending coronary artery (24/26; 92 percent), compared with group 1 (2/15 and 10/15, respectively) and group 2 (6/18 and 12/18, respectively). Group 3 also manifested more extensive disease than groups 1 and 2 (judged by scoring system of Friesinger et al), with a score of 11 or more in 18 of 26 patients. We conclude that marked depth of "ischemic" ST-segment depression aids in identifying that subgroup of the coronary population with severe coronary artery disease and, therefore, serves as a useful means of culling out patients with a potentially serious prognosis who might benefit from intensive diagnostic or therapeutic interventions.

Coronary Disease↗
PubMed1976

Treadmill stress tests as indicators of presence and severity of coronary artery disease.

The configuration, time of onset, and duration of depressed ST segments during and after treadmill exercise testing were evaluated in 269 patients with angiographically proven coronary artery disease and 141 normal subjects. The test specificity was 93% and sensitivity 64%, the latter being influenced by the type of ST response; false-positive responses were rare with depressed, downsloping STs (1 of 123, 1%), occurred more frequently with horizontal ST depression (9 of 60, 15%), and occurred commonly with slowly upsloping STs (15 of 47, 32%). Depressed downsloping STs, ischemic changes appearing in the first 3 minutes of exercise, and those persisting past 8 minutes in recovery were associated with 91%, 86%, and 90% prevalences of two- to three-vessel or main left coronary disease, respectively. It is concluded that attention to configuration, time of onset, and duration of ischemic ST depression aids both in assessing the validity of exercise responses in diagnosing coronary artery disease and in delineating patients with advanced coronary obstruction.

Adult↗
PubMed1975

Sound envelope averaging and the differential diagnosis of systolic murmurs.

Phonocardiography previously has been limited in scope because the attained suboptimal signal-to-noise ratio has interfered with the sensitivity and clarity of recordings. A new system is described that reduces this problem by utilizing demodulation and synchronous averaging of the "envelop" of cardiac sounds. A limited survey of the differential diagnostic capabilities of this technique is presented for 80 patients having one of six common forms of pathological systolic murmurs and an 89 per cent diagnostic accuracy is demonstrated. This system promises to be a valuable noninvasive adjunct in cardiologic diagnosis research and education.

Diagnosis, Differential↗
PubMed1975

ST-segment isolation and quantification as a means of improving diagnostic accuracy in treadmill stress testing.

A new method of ST-segment analysis utilizing computer-analytic techniques has been employed in treadmill exercise testing, with the aim of enhancing diagnostic sensitivity and specificity. One hundred thirty-three individuals were studied, including 62 normal subjects (Group I), 29 patients with coronary disease and clear, "ischemic" ST-segment responses to exercise testing (Group II), and 42 patients with coronary disease but normal or nondiagnostic exercise tests (Group III). The techniques used included: computer averaging, to minimize motion artifact and baseline drift; a means of isolating the ST-segment from the T-wave and quantifying ST-amplitude and slope (the isolated ST integral, IST); and the relating of the IST to a given heart rate, thus taking cognizance of the dependency of ST-depression on heart rate and level of exercise. These methods resulted in a test specificity exceeding 90 per cent and a sensitivity of over 85 per cent. Further evidence of the improved sensitivity achieved using these techniques included a 79 per cent (33 of 42) recognition of abnormalities in Group III, patients having normal or nondiagnostic visually interpreted treadmill stress tests (i.e., no flat or downsloping ST-segments of 1 mm. or greater). Moreover, 15 of 29 patients in Group II (52 per cent) manifested abnormal IST's before development of a typical "ischemic" ST, and in 17 patients (59 per cent), the IST continued to remain positive after disappearance of the characteristic flat or downsloping ST-segment. It is concluded that this type of computation analysis adds appreciable diagnostic sensitivity and specificity to treadmill stress testing.

Adult↗
PubMed1975

Effect of clofibrate on progression of coronary disease: a prospective angiographic study in man.

Lowering blood lipids has been invoked as a means of controlling future coronary events. In this prospective study, the effect of a lipid-reducing agent clofibrate (2 gm. daily) on extent of coronary artery disease was investigated. Forty patients, 32 having aortocoronary bypass, six having Vineberg operations, two having neither, were placed double-blind in placebo (24 patients) and clofibrate (16 patients) groups, and restudied by selective coronary angiography one year later. An additional 24 patients dropped from the study due to adverse drug reactions in eight. Each patient's right, left, anterior descending, and circumflex coronary arteries (with their branches) were separately rated according to degree of obstruction. The clofibrate group showed a significantly greater fall in triglyceride than did the placebo group (minus 13.7 per cent versus plus 2.3 per cent; p equal to 0.45). In the clofibrate group, 19 out of 64 coronary arteries (29.6 per cent) showed progressive coronary narrowing, not significantly different from the placebo group (24 out of 96 coronary arteries narrowed, 25 per cent; p equal to 0.26). No significant differences between drug groups emerged when the data were corrected for degree of fall of blood lipids, initial lipoprotein type, or effect in bypassed versus nonbypassed vessels (p always greater than 0.2). Regression of coronary artery disease was not seen. We conclude that clofibrate did not significantly influence the rate of progression of coronary artery disease in a one-year period.

Arteriosclerosis↗
PubMed1975

Inefficacy of "therapeutic" serum levels of digoxin in controlling the ventricular rate in atrial fibrillation.

Although therapeutic and toxic serum concentrations of digoxin have been established, there is sparse information permitting correlation of drug level with clinical effect. This study was undertaken to assess the radioimmunoassay serum digoxin levels in 30 patients with acute atrial fibrillation (38 determinations) and 30 patients with chronic atrial fibrillation (54 determinations). Those with chronic fibrillation were subdivided into those in clinically stable condition (14 patients), and those seriously ill and in clinically unstable condition (16 patients). Slowing of ventricular rate in patients with stable, chronic atrial fibrillation was accomplished in 10 of 16 instances by "therapeutic" and "subtherapeutic" levels of digoxin (less than 2 ng/ml). Ventricular rate was "controlled" (65 to 95 beats/min) with therapeutic levels of serum digoxin in only five instances of acute atrial fibrillation and seven of unstable chronic atrial fibrillation. In 43 studies (23 of acute atrial fibrillation, 20 of chronic atrial fibrillation), a rapid ventricular rate (95 to 140 beats/min) persisted in the presence of "therapeutic" or high levels of digoxin. Thirty-nine of these were in patients who were seriously ill with conditions such as infection, hypoxia or recent thoracotomy. Slowing of the ventricular rate required "toxic" concentrations of digoxin (2.5 to 6 ng/ml) in 15 instances. We conclude that sufficient amounts of digoxin to achieve "therapeutic" serum concentrations may fall to lower the ventricular rate in atrial fibrillation to less than 100 beats/min, especially when a serious, complicating illness coexists.

Atrial Fibrillation↗
PubMed1975

Variability of hemodynamic responses to acute digitalization in chronic cardiac failure due to cardiomyopathy and coronary artery disease.

Eight patients with chronic congestive heart failure (four with cardiomyopathy and four with ischemic heart disease) underwent hemodynamic studies during acute administration of digoxin, given intravenously in two 0-5 mg doses 2 hours apart. Observations were made before administration of digitalis (control period) and serially therafter for 4 hours after the first dose. Resting mean cardiac index and pulmonary arterial wedge pressure were as follows: 2.0 liters/min per m2 and 23 mm Hg (control period); 2.1 and 24 (at 1 hour); 2.0 and 23 (at 2 hours); 2.7 and 19 (at 3 hours); and 2.3 and 20 (at 4 hours). Exercise responses of mean cardiac index and pulmonary arterial wedge pressure in five patients were: 3.1 liters/min per m2 and 36 mm Hg (control period); 3.2 and 33 (at 1 hour); 3.2 and 28 (at 2 hours); 3.1 and 27 (at.3 hours); and 3.4 and 31 (at 4 hours). The pulmonary arterial wedge pressure remained elevated during exercise in all cases. Arrhythmias were seen in five patients after administration of 0.5 mg of digoxin. Hemodynamic improvement at 4 hours involving both reduced filling pressure and increased blood flow was observed in only two patients at rest and in one additional patient during exercise. Acute deterioration of cardiac function (elevated pulmonary arterial wedge pressure of decreased cardiac index) occurred 30 minutes after administration of digoxin in four patients, concomitantly with increased systemic resistance. In six patients, a peak hemodynamic effect appeared 1 to 1 1/2 hours after administration of digoxin, with partial or total loss of initial benefit by 2 and 4 hours. In previously performed studies observations have seldom exceeded 1 hour; the results of this 4 hour study suggest that, in patients with cardiomyopathy or coronary artery disease and chronic congestive heart failure, acute digitalization does not necessarily lead to consistent, marked or lasting hemodynamic improvement. Thus, current concepts of the use of digitalis is such patients may require revision.

Adult↗