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Biomedical subjects

K M Kent

Publications and source records attributed to K M Kent.

At least 271 records · Page 15Linked to original sources
PubMed1979

Left ventricular function at rest and during exercise after aortic valve replacement in patients with aortic regurgitation.

To determine the effect of aortic valve replacement on reversing abnormalities of left ventricular function in patients with aortic regurgitation, radionuclide cineangiography was used to study 16 sympatomatic patients with aortic regurgitation before and 6 months after aortic valve replacement. Before operation, left ventricular ejection fraction was 46 +/- 3 percent at rest (normal mean +/- standard error of the mean 57 +/- 1 percent; P less than 0.001), and decreased to 37 +/- 4 percent during exercise (normal 71 +/- 2 percent; P less than 0.001). after operation, ejection fraction rose to 58 +/- 4 percent at rest, indistinguishable from the normal value, and during exercise was 53 +/- 4 percent, increased (P less than 0.001) from before operation but significantly (P less than 0.001) subnormal. Thus, aortic valve replacement can improve but usually does not normalize left ventricular function during exercise in symptomatic patients with aortic regurgitation.

Adult↗
PubMed1979

Syndrome of valvular pulmonary stenosis and valvular aortic stenosis with atrial septal defect.

Clinical and morphological findings are described in 2 adults with combined valvular pulmonary and aortic stenosis with atrial septal defect, an extremely rare combination of lesions. The direction of the shunt via the atrial septal defect in this combination appears to be dependent on the relative degree of outflow obstruction on the right side compared with the left side of the heart. In 1 patient the degree of obstruction at the pulmonary valve was nearly three times that at the aortic valve and, therefore, the shunt was right to left and the patient was severely cyanotic. In the other patient, the degree of obstruction at the pulmonary valve was slightly less than that at the aortic valve and, therefore, the shunt was entirely left to right and the patient was acyanotic. Diagnosis of an associated obstructive lesion on the left side of the heart in a patient with an obstructive lesion on the right side of the heart is essential because operative relief of the right-sided obstruction without relief of the left-sided obstruction may lead to rapid, fatal pulmonary congestion.

Adult↗
PubMed1979

Effect of septal myotomy and myectomy on left ventricular systolic function at rest and during exercise in patients with IHSS.

Patients with idiopathic hypertrophic subaortic stenosis (IHSS) have supernormal left ventricular systolic function at rest. Septal myotomy/myectomy reduces outflow obstruction and symptoms. However, it has been proposed that operation causes myocardial damage, with consequent reduction in left ventricular function and potentially deleterious long-term consequences, despite relief of symptoms. To evaluate the effect of myotomy and mylectomy on left ventricular function, we employed noninvasive radionuclide cineangiography at rest and during maximal exercise in21 consecutive patients with IHSS, before and 6 months after operation. In 30 normal subjects, the ejection fraction (EF) was 57 +/- 2% at rest and 71 +/- 2% during exercise. Before operation in patients with IHSS, the EF was supernormal at rest (76 +/- 2%, p less than 0.001), and normal during exercise (71 +/- 3%, NS). All patients improved from NYHA functional class III-IV preoperatively to class I-II postoperatively; the maximal provocable gradient invariably diminished (average, 100 +/- , mm Hg preop, 33 +/- 9 mm Hg postop, p less than 0.001). Postoperatively, the EF at rest was 67 +/- 2%, still supernormal, but less than that noted preoperatively (p less than 0.001). During exercise, the EF was 66 +/- 4%, only mildly diminished (p less than 0.01) from that preoperatively. We conclude that muscle resection during myotomy and myectomy usually does not cause any important impairment of global left ventricular function at rest or during exercise stress.

Adolescent↗
PubMed1979

Verapamil therapy: a new approach to the pharmacologic treatment of hypertrophic cardiomyopathy. I. Hemodynamic effects.

The hemodynamic effects of intravenous verapamil administration were examined in 27 patients with hypertrophic cardiomyopathy. Increasing doses of verapamil produced small increases in heart rate and cardiac output and a significant decrease in systolic blood pressure, but had no significance effect on mean pulmonary artery wedge pressure or left ventricular end-diastolic pressure. The highest dose of verapamil increased heart rate from 72 +/- 3 to 81 +/- 6 beats/min and reduced systolic blood pressure from 118 +/- 8 to 99 +/- 5 mm Hg (p less than 0.005). This dose decreased the basal left ventricular outflow tract gradient from 94 +/- 14 to 49 +/- 14 mm Hg and the average left ventricular outflow tract gradient during the Valsalva maneuver from 76 +/- 5 to 63 +/- 13 mm Hg, during amyl nitrite inhalation from 69 +/- 15 to 39 +/- 13 mm Hg, and during isoproterenol infusion from 108 +/- 29 to 70 +/- 21 mm Hg (p less than 0.01). These results indicate that verapamil can significantly decrease left ventricular outflow obstruction in patients with hypertrophic cardiomyopathy and thus may provide an important new therapeutic agent in the treatment of this disorder.

Adult↗
PubMed1979

Coronary artery narrowing in coronary heart disease: comparison of cineangiographic and necropsy findings.

Of 10 patients with fatal coronary heart disease undergoing coronary angiography 0 to 69 d (average, 21) before necropsy, the amount of narrowing in 61 coronary arteries observed angiographically (diameter reduction) during life by three angiographers was compared with that observed histologically (cross-sectional area) at necropsy. No overestimations of the degree of narrowing were made angiographically. Of 11 coronary arteries or their subdivisions narrowed 0 to 50% in cross-sectional area histologically, none were underestimated angiographically; of eight narrowed 51% to 75% histologically, seven had been underestimated, and of 42 narrowed 76% to 100% histologically, 17 were underestimated angiographically. The coronary atherosclerotic plaquing was diffuse (greater than 25% cross-sectional area narrowing) in 90% of 467 five-millimetre segments of coronary artery examined (24 cm per patient), and this diffuseness of the atherosclerotic process seems to be the major reason for angiographic underestimation of coronary narrowings.

Adult↗
PubMed1978

Effects of coronary-artery bypass on global and regional left ventricular function during exercise.

To determine the effect of coronary revascularization on exercise-induced abnormalities of left ventricular-ejection fraction and regional contraction, we obtained electrocardiograph-gated 99mTc radionuclide cineangiograms before and after operation in 23 consecutive patients. At rest, their average ejection fraction remained unchanged: 51 +/- 3 versus 54 +/- 4 per cent (+/- S.E.M.). However, 17 of the patients showed improvement of ejection fraction during postoperative exercise (increase of 51 per cent). The remaining six patients had no change or a decreased ejection fraction during exercise. All patients with improved ejection fractions during exercise were symptomatically improved. No improvement of regional function occurred at rest, but improvement did occur in regions of exercise-induced dysfunction. Although coronary revascularization has little effect on left ventricular function at rest, the ejection fraction during exercise and exercise-induced wall-motion abnormalities improve in most patients who experience symptomatic improvement.

Adult↗
PubMed1978

Long-term anatomic fate of coronary-artery bypass grafts and functional status of patients five years after operation.

To assess long-term results, coronary and graft angiography was performed 53 to 84 months after operation in 22 of 30 consecutive patients who had undergone coronary-artery bypass grafting before 1973, and who had at least one graft patent at an early (three to nine months) postoperative study. Of the 33 grafts, 31 were patent at late study. All patients had severe symptoms before operation. Of 16 who became asymptomatic early after operation, angina pectoris later redeveloped in 11. Progression of disease in ungrafted vessels accounted for symptomatic deterioration in nine of these 11 patients. We conclude that most grafts patent several months after operation remain so for at least 4 1/2 years, and that although most patients improve symptomatically after operation, symptomatic deterioration is common in the succeeding years and is most often due to progression of disease in ungrafted vessels.

Angina Pectoris↗
PubMed1978

Exercise-induced left ventricular dysfunction in symptomatic and asymptomatic patients with aortic regurgitation: assessment with radionuclide cineangiography.

In patients with aortic regurgitation,, left ventricular dysfunction at rest, which is associated with a poor long-term prognosis, often develops before severe symptoms. To determine whether evidence of left ventricular dysfunction could be detected before it appeared at rest, 43 patients with severe aortic regurgitation were studied using radionuclide cineangiography during exercise. In 30 normal subjects, left ventricular ejection fraction increased during exercise (57 +/- 1 percent [mean +/- standard error] at rest, 71 +/- 2 percent during exercise, P less than 0.001). In contrast, among 21 symptomatic patients, ejection fraction was normal at rest in 14 patients (average 47 +/- 2 percent) but normal during exercise in only one patient (average 38 +/- 2 percent, P less than 0.001). Ejection fraction was normal at rest in 21 of 22 asymptomatic patients (average 62 +/- 2 percent) but was normal during exercise in only 13 (average 57 +/- 3 percent, P less than 0.001). Thus, exericse-induced left ventricular dysfunction can precede symptoms and dysfunction at rest. Radionuclide assessment of left ventricular function during exercise may prove valuable in sequentially following the state of left ventricular function in patients before the onset of symptoms or of irreversible left ventricular failure.

Adolescent↗
PubMed1978

Effect of nitroglycerin on exercise-induced abnormalities of left ventricular regional function and ejection fraction in coronary artery disease. Assessment by radionuclide clineagiography in symptomatic and asymptomatic patients.

The effects of nitroglycerin (TNG) on exercise-induced abnormalities of left ventricular wall motion and ejection fraction are unknown in symptomatic and asymptomatic patients with coronary artery disease (CAD). In the present investigation radionuclide cineangiographic studies were performed in 47 patients with CAD (14 without angina during exercise) and in 25 normal subjects. All CAD patients, including those without symptoms, demonstrated regional wall motion abnormalities during exercise. In all patients, ejection fraction (EF) also responded abnormally to exercise: EF decreased from 48% at rest to 36% during exercise (P less than 0.001). EF increased in all normal subjects from an average of 58% at rest to 71% during exercise (P less than 0.001). In all CAD patients TNG reduced exercise-induced regional wall abnormalities and increased EF attained during exercise from an average of 36 to 48% (P less than 0.001). EF in normal subjects was unchanged by TNG. Thus, exercise can cause abnormalities in left ventricular regional function and ejection fraction in patients with or without symptoms; these abnormalities can be mitigated by prophylactic TNG.

Adult↗
PubMed1978

Long-term clinical course and symptomatic status of patients after operation for hypertrophic subaortic stenosis.

Long-term results of operation for IHSS were reviewed in 124 patients operated upon between 1960 and 1975. Most patients improved symptomatically and manifested marked reduction in LV outflow gradient at rest postoperatively. However, ten (8%) patients died of causes related to operation, 14 (12%) had persistent or recurrent severe functional limitation, and 11 (9%) died up to 13 years postoperatively due to hypertrophic cardiomyopathy. Overall annual mortality rate was 3.5% and was 1.8% for late deaths alone. Of 11 late postoperative deaths, six were sudden and five were due to chronic heart failure. Atrial fibrillation was significantly more common in patients who died late postoperatively than in survivors. Nine of the 11 late deaths had associated medical problems that may have contributed to their outcome. In conclusion, long-lasting clinical improvement occurred in most patients who survived operation for IHSS. However, 12% of patients deteriorated clinically over the 5.2 year average follow-up, and there is continued, small annual mortality.

Adolescent↗
PubMed1978

Long-term hemodynamic and electrocardiographic assessment following operative repair of tetralogy of Fallot.

To evaluate the long-term results of operative repair of tetralogy of Fallot, the cardiovascular, clinical, and electrocardiographic status was evaluated in 21 patients who had undergone operation 5 to 19 years previously. All patients were asymptomatic. Major functional abnormalities detected were enlarged right ventricular dimension in 15 of 17 patients, and elevated right ventricular systolic pressure during maximal exercise (mean, 69 +/- 5 mm Hg). Nevertheless, all patients had normal or nearly normal cardiovascular responses to maximal exercise as measured by cardiac output, maximal oxygen consumption, and left ventricular ejection fraction. Significant ventricular arrhythmias were detected during 24-hour ambulatory monitoring in 14 of 21 patients. Multiform ventricular premature beats (VPBs) were seen in 13 of 14 patients, couplets in four patients, greater than 30 VPBs for at least 1 hour in three, 4-complex ventricular tachycardia in one, and repeated R on T episodes in one. Although clinical and hemodynamic function was excellent in most patients, close follow-up is still necessary to determine the significance of the high-grade ventricular arrhythmias detected and if late manifestations of cardiovascular deterioration will occur.

Cardiac Catheterization↗
PubMed1978

Contractile damage from reperfusion after transient ischemia in the dog.

The patterns of regional contractile function were examined with ultrasonic crystals in "open-chest" anesthetized dogs. In normal myocardium, the base-line end-diastolic segment length (EDL) was 1.63 +/- 0.12 cm. and the mean systolic length (MSL) was 1.47 +/- 0.17 cm. Mean velocity of shortening over the first one third of systole (V1/3) was 15.9 +/- 2.3 mm. per second. Coronary occlusion induced regional ischemia with segmental dyskinesia (MSL = 1.84 +/- 0.12 cm). Reperfusion after 5 or 10 minutes of occlusion induced rapid recovery of contractile function that was independent of catecholamine release, as demonstrated in animals pretreated with 6-OH dopamine. After initial recovery, however, contractile function deteriorated. There were an increase in EDL (from 1.73 +/- 0.11 to 1.78 +/- 0.11; p less than 0.001) and the appearance of early systolic dyskinesia. V1/3 diminished from 5.6 +/- 4.6 to -6.6 +/- 2.5 mm. per second (p less than 0.005). Thus reperfusion damage, defined as late deterioration after recovery from brief periods of ischemia, may be partly distinct from ischemic damage per se. It is possible that the deterioration of myocardial function which accompanies reperfusion of previously ischemic myocardium may be a contributing factor in the transient myocardial dysfunction that is occasionally seen following cardiopulmonary bypass.

Animals↗
PubMed1977

Acute coronary occlusion: prolonged increase in collateral flow following brief administration of nitroglycerin and methoxamine.

Regional coronary blood flow was determined with the radioactive microsphere technique 10 an 70 minutes and 2 1/2 and 5 hours after abrupt occlusion of the left anterior descending coronary artery in 12 closed chest sedated dogs. In six dogs, nitroglycerin, 200 to 400 microng/min, was infused intravenously 10 to 70 minutes after occlusion. Methoxamine was administered to return blood pressure and heart rate to prenitroglycerin levels. Ten minutes after occlusion (before treatment) collateral flow values and ischemic zone endocardial/epicardial flow ratios were equivalent in untreated (0.11+/-0.03 ml/min per g; 0.31+/-0.05) and treated dogs (0.14+/-0.02 ml/min per g; 0.29+/-0.03). In untreated dogs, collateral flow did not change over 5 hours; the endocardial/epicardial flow ratio was decreased at 5 hours (0.21+/-0.05, P less than 0.05). In contrast, in treated dogs, collateral flow and the endocardial/epicardial flow ratio were increased at 70 minutes (0.27+/-0.04 ml/min per g, P less than 0.05; 0.53+/-0.10, P less than 0.05). Most importantly, collateral flow remained elevated 5 hours after occlusion (0.26+/-0.03 ml/min per g, P less than 0.05) although treatment was discontinued 70 minutes after occlusion. Hence, collateral flow was unchanged over 5 hours of occlusion in untreated dogs, but short-term treatment with nitroglycerin and methoxamine resulted in a sustained increase in collateral flow. These findings may be a result of stimulation by nitroglycerin and methoxamine of the spontaneous rate at which intrinsic collateral function increases after ischemia. Alternatively, nitroglycerin and methoxamine may maintain cell viability until collateral vessels develop spontaneously.

Animals↗