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Biomedical subjects

K M Kent

Publications and source records attributed to K M Kent.

At least 253 records · Page 14Linked to original sources
PubMed1982

Improved left ventricular diastolic filling in patients with coronary artery disease after percutaneous transluminal coronary angioplasty.

Left ventricular (LV) diastolic filling is abnormal at rest in many patients with coronary artery disease (CAD), even in the presence of normal resting LV systolic function. To determine the effects of improved myocardial perfusion on impaired. LV diastolic filling, we studied 25 patients with one-vessel CAD by high-temporal-resolution radionuclide angiography before and after percutaneous transluminal coronary angioplasty (PTCA). No patient had ECG evidence of previous myocardial infarction. Despite normal regional and global LV systolic function at rest in all patents, LV diastolic filling was abnormal (peak LV filling rate [PFR] less than 2.5 end-diastolic volumes (EDV)/sec or time to PFR greater than 180 msec) in 17 of 25 patients. Twenty-three patients had abnormal LV systolic function during exercise. After successful PTCA, LV ejection fraction and heart rate at rest were unchanged, but LV ejection fraction during exercise increased, from 52 +/- 8% (+/- SD) to 63 +/- 5% (p less than 0.001). LV diastolic filling at rest improved: PFR increased from 2.3 +/- 0.6 to 2.8 +/- 0.5 EDV/sec (p less than 0.001) and time to PFR decreased from 181 +/- 22 to 160 +/- 18 msec (p less than 0.001). Thus, a reduction in exercise-induced LV systolic dysfunction after PTCA, reflecting a reduction in reversible ischemia, was associated with improved LV diastolic filling at rest. These data suggest that in many CAD patients with normal resting LV systolic function and without previous infarction, abnormalities of resting LV diastolic filling are not fixed, but appear to be reversible manifestations of impaired coronary flow.

Adult↗
PubMed1981

Aortic valve replacement without myocardial revascularization in patients with combined aortic valvular and coronary artery disease.

To test the hypothesis that coronary artery bypass grafting (CABG) is not routinely required in patients undergoing aortic valve replacement (AVR) who have coexistent coronary artery disease (CAD), we compared the results of operation in 55 consecutive symptomatic patients who had CAD and underwent AVR without CABG with results in another 142 patients without CAD who underwent AVR during the same period, and with published results from other centers in which CABG was used in patients with CAD who underwent AVR. Operative mortality was 4% in patients with CAD and 5% in patients without CAD. Late survival was not significantly different between the two groups when analyzed for the entire population (80% survival at 3 years in CAD patients, 82% for non-CAD patients), or for the subgroup of patients with aortic stenosis, aortic regurgitation or aortic stenosis plus regurgitation. Eight patients with CAD (15%) developed recurrent angina after AVR (mean follow-up 43 months); only three patients (6%) required CABG because of medically refractory angina (12-43 months). Operative mortality, operative infarction (9%), recurrent angina and long-term survival in patients with CAD after AVR were similar to those at other centers after AVR plus CABG. These data suggest that preoperative detection of CAD does not necessitate CABG in all patients at the time of AVR.

Adult↗
PubMed1981

Accuracy of angiographic determination of left main coronary arterial narrowing. Angiographic--histologic correlative analysis in 28 patients.

To evaluate the accuracy of coronary angiography in identifying severe narrowing of the left main coronary artery (LMCA), the degree of narrowing observed by angiography was compared to that observed at necropsy in 28 patients with symptomatic coronary heart disease in whom angiography had been performed within 40 days of death. The angiograms were evaluated independently by three experienced angiographers. In 20 of the 28 patients (71%), the degree of narrowing of the LMCA was either underestimated (13 patients) or overestimated (10 patients) by two or three of three angiographers; of 84 angiographic judgments made by the three angiographers in the 28 patients, 54 (64%) were underestimates (33 judgments, 39%) or overestimates (21 judgments, 25%) of the degree of LMCA narrowing. Of 12 LMCAs narrowed 76-100% in cross-sectional area at necropsy, six were underestimated at preoperative angiography by two or three of three angiographers; of 12 LMCAs narrowed 51-75% in cross-sectional area at necropsy, all 12 were either under- or overestimated angiographically by two or three of three angiographers; of four LMCAs narrowed 26-50% in cross-section at necropsy, two were overestimated by two of three angiographers. Thus, angiographic determination of degrees of narrowing of the LMCA during life is subject to considerable error. The angiographic errors appear to have resulted primarily from the presence of atherosclerotic plaque in the LMCA and an insufficient number of angiographic projections.

Adult↗
PubMed1981

Impaired left ventricular diastolic filling in patients with coronary artery disease: assessment with radionuclide angiography.

To assess left ventricular (LV) diastolic filling at rest in patients with coronary artery disease (CAD), we analyzed high-resolution time-activity curves (10-20 msec/frame) obtained from gated radionuclide angiograms in 231 patients. Peak LV filling rate (PFR), expressed in end-diastolic volumes per second (EDV/sec), was subnormal in CAD patients (1.8 +/- 0.6 [+/- SD] vs normal mean of 3.3 +/- 0.6, p les than 0.001) and time to PFR (TPFR), measured from end-systole to PFR, was prolonged (171 +/- 41 msec vs normal mean of 136 +/- 23 msec, p less than 0.001). These indexes were also abnormal in the 141 patients with normal resting LV ejection fraction (PFR = 2.1 +/- 0.5 EDV/sec; TPFR = 175 +/- 36 msec) and in 123 patients without Q waves on the ECG (PFR = 2.1 +/- 0.5 EDV/sec; TPFR = 168 +/- 38 msec). Abnormal LV filling at rest (PFR less than 2.5 EDV/sec or TPFR greater than 180 msec) was found in 91% of all patients with CAD, 86% of patients with normal resting LV ejection fractions, 85% of patients without Q waves, and 82% of patients with normal resting LV ejection fraction, no resting regional wall motion abnormalities and no Q waves. Thus, LV diastolic filling, evaluated noninvasively by radionuclide angiography, is abnormal in a high percentage of patients with CAD at rest independent of LV systolic function or previous myocardial infarction.

Adult↗
PubMed1981

Long-term hemodynamic assessment of the porcine heterograft in the mitral position. Late development of valvular stenosis.

We undertook a study of patients who had porcine mitral valves in place for more than 5 years and who had no clinical signs or symptoms suggestive of valve dysfunction. Of the first 54 patients who had porcine valves implanted in the mitral position, 18 were available for catheterization; all had a routine hemodynamic study postoperatively (mean 7 months) for comparison. Mean follow-up was 85 months (range 61-111 months). Compared with the early postoperative data, there was a significant increase in mean mitral valve gradient, from 5.9 +/- 0.7 to 8.6 +/- 0.7 mm Hg (p less than 0.01), and a significant decrease in calculated mitral valve area, from 2.2 +/- 0.2 to 1.7 +/- 0.2 cm2 (p less than 0.01). Moreover, seven patients showed a decrease in valve area greater than 1.0 cm2, five with valves in place for more than 80 months and only two of 11 patients with valves in place for 80 months or less (p less than 0.05). We conclude that there is a significant incidence of hemodynamic deterioration of porcine heterografts in the mitral position for greater than 5 years, even in patients who are clinically stable.

Adolescent↗
PubMed1981

Effects of verapamil on left ventricular systolic function and diastolic filling in patients with hypertrophic cardiomyopathy.

Verapamil improves exercise capacity in patients with hypertrophic cardiomyopathy (HCM), but its mechanism of action are unknown. We examined the effects of oral verapamil (320-480 mg/day) on resting left ventricular (LV) systolic and diastolic function in patients with HCM. High-temporal-resolution time-activity curves from gated technetium-99m radionuclide angiograms were analyzed before and after verapamil therapy in 40 patients, of whom 16 were also studied during propranolol therapy (80-960 mg/day). All but one patient had normal or supranormal systolic function, but 70% had evidence of diastolic dysfunction, defined as peak LV filling rate (PFR) less than 2.5 end-diastolic volumes (EDV)/sec or time to PFR greater than 80 msec. Verapamil did not change LV ejection fraction, peak ejection rate or ejection time, but did increase PFR (control 3.3 +/- 1.0 EDV/sec, verapamil 4.1 +/- 1.1 EDV/sec; p less than 0.001) and reduce time to PFR (control 187 +/- 56 msec, verapamil, 159 +/- 34 msec; p less than 0.001). Only 30% of patients had evidence of diastolic dysfunction during verapamil. In contrast, propranolol did not change LV ejection fraction, PFR or time to PFR, but did prolong ejection time and reduce peak ejection rate. Thus, LV diastolic filling is abnormal in a high percentage of patients with HCM, and verapamil normalizes or improves these abnormalities without altering systolic function. This mechanism may contribute to the clinical improvement of many HCM patients during verapamil therapy.

Adolescent↗
PubMed1981

Hemodynamic function of the Hancock standard orifice aortic valve bioprosthesis.

Reports that the hemodynamic performance of the standard orifice aortic bioprosthesis in less than optimal have prompted recommendations that mechanical prosthesis or anulus-enlarging procedures be used in adult patients with a small aortic root. The hemodynamic function of the Hancock bioprosthesis was evaluated in 77 patients who underwent cardiac catheterization of rest and with isoproterenol infusion (15 patients) an average of 6 months after operation. The average peak systolic gradient (basal conditions) was 7 mm Hg (range 0 to 37 mm Hg); 35 patients had no resting gradient. Fifteen patients received 21 mm diameter valves and had an average systolic valve gradient of 10 mm Hg (range 0 to 30 mm Hg); the average effective valve orifice area was 1.27 +/- 0.17 cm2 for 21 mm, 1.46 +/- 0.11 cm2 for 23 mm, 1.72 +/- k0.20 cm2 for 25 mm, and 1.97 +/- 0.06 for 27 mm bioprostheses. Isoproterenol infusion, elevating cardiac output 66%, increased the peak systolic gradient from an average of 11 mm Hg (range 0 to 37 mm Hg) to 44 mm Hg (range 10 to 85 mm Hg). It is concluded that small-diameter (21 and 23 mm) Hancock bioprostheses can be used with acceptable clinical and hemodynamic function in patients with a small body surface area.

Adult↗
PubMed1980

Frequency and direction of interatrial shunting in valvular pulmonic stenosis with intact ventricular septum and without left ventricular inflow or outflow obstruction. An analysis of 127 patients treated by valvulotomy.

This report summarizes observations in 127 patients who underwent pulmonic valvulotomy for valvular pulmonic stenosis with intact ventricular septum and without obstruction to left ventricular inflow or outflow. Of the 127 patients, 30 (24%) preoperatively by dye dilution curves had shunting at the atrial level: in 19 (63%), the shunt was right-to-left, and in the other 11 (27%), entirely left-to-right. The patients with right-to-left interatrial shunts had severe pulmonic valve stenosis (average peak systolic pressure gradient = 120 +/- 11 mm. Hg) and small (average diameter 1.1 +/- 0.1 cm.) sized defects in the atrial septum (patent foramen ovale). In contrast, the patients with left-to-right shunts had mild to moderate pulmonic valve stenosis (average peak systolic pressure gradient = 60 +/- 5 mm. Hg) and relatively large (average diameter = 2.8 +/- 0.1 cm.) defects in the atrial septum (true atrial septal defect). The patients with right-to-left interatrial shunts had no significant differences in right versus left atrial pressures. The patients with left-to-right interatrial shunts, however, had left atrial pressures significantly greater than right atrial pressures (7 +/- 0.5 vs 5 +/- 0.5, p less than 0.05). No significant differences were found in ventricular end-diastolic pressures.

Adolescent↗
PubMed1980

Left ventricular myotomy and myectomy in patients with obstructive hypertrophic cardiomyopathy and previous cardiac arrest.

Left ventricle myotomy and myectomy was carried out in nine patients with obstructive hypertrophic cardiomyopathy solely because of a previously documented episode of cardiac arrest. Before cardiac arrest, each patient had either no or only minimal functional limitation and therefore would not have met the usual criteria for operation, namely, severe symptoms unresponsive to medical therapy. Of the nine patients, one died in the perioperative period, and one died suddenly and unexpectedly 9 months postoperatively. The remaining seven patients have survived 9 months to 5.5 years after operation; six of the seven are asymptomatic and one has only mild symptoms. Operation resulted in a marked decrease or abolition of the left ventricular outflow gradient under basal conditions in seven of the eight patients studied postoperatively. Significant residual outflow obstruction was demonstrated after operation in the patient who later died. Sudden death in patients with obstructive hypertrophic cardiomyopathy appears usually to result from ventricular arrhythmia, and prevention of recurrent fatal arrhythmia is the goal of treatment in patients who have had cardiac arrest and have been resuscitated. Such patients should be treated indefinitely with antiarrhythmic drugs. In addition, when severe outflow obstruction is present, we postulate that effective operative relief of obstruction and consequent reduction of left ventricular systolic pressure will provide additional protection.

Adolescent↗
PubMed1980

Observations on the optimum time for operative intervention for aortic regurgitation. I. Evaluation of the results of aortic valve replacement in symptomatic patients.

Fifty consecutive patients undergoing aortic valve replacement for isolated aortic regurgitation were studied prospectively by echocardiography, electrocardiography and cardiac catheterization. Good quality echocardiograms were obtained in 49 of the 50 patients. Left ventricular (LV) dilatation was present in all 49 patients. LV systolic function, as assessed by echocardiographic percent fractional shortening, was normal in many patients but was moderately to severely reduced (less than 25%) in 14 patients (29%). Echocardiographic studies 6 months postoperatively revealed significant reductions in LV end-diastolic dimension (73.8 mm vs 58.7 mm; p less than 0.01), and serial echocardiographic studies early and late after operation revealed that the decrease in LV size had occurred by the time of the early study (8-22 days postoperatively), with little additional change thereafter. Operative deaths occurred in three of the 49 patients (6%). Eight of the 49 patients (16%) died of congestive heart failure (CHF) after hospital discharge at times ranging from 5-43 months after operation. Preoperative echocardiographic measurements of the LV end-systolic dimension and percent fractional shortening were strongly associated (p less than 0.01) with these late CHF deaths. Preoperative LV end-systolic dimension greater than 55 mm and fractional shortening less than 25% identified the high-risk group: nine of 13 patients (69%) in this group died either at operation or subsequently from CHF. In contrast, of 32 patients with LV end-systolic dimension less than 55 mm, only one died at operation and one died late from CHF. Thus, the population at high risk of late death from CHF was identified before operation by echocardiography.

Adult↗
PubMed1980

Evaluation of aortic valve replacement in patients with valvular aortic stenosis.

Echocardiographic and hemodynamic studies were obtained in 42 consecutive patients undergoing aortic valve replacement for isolated aortic stenosis. Concentric left ventricular (LV) wall thickening, the most common preoperative abnormality, occurred in 95% of patients. LV dilation with reduced fractional shortening was noted in approximately 25% of patients but was severe in only one patient. Six months after operation, LV wall thickness had decreased on average but had not returned to normal and fractional shortening was unchanged. Repeat measurements in 13 patients an average of 37 months after operation were unchanged compared with measurements made 6 months after operation. When patients were subdivided into those with LV dilatation and those without, we found that patients with dilated ventricles preoperatively had a greater decrease in LV internal dimension and mass than those without preoperative dilatation. The patient data also were examined for possible association with mortality. One operative (2%) and five late cardiac (13%) deaths occurred. No preoperative or 6-month postoperative echocardiographic or hemodynamic measurement was strongly associated with these deaths, nor were any late deaths due to congestive heart failure. Compared with preoperative measurements in symptomatic patients who were operated for isolated aortic regurgitation, patients with aortic stenosis had smaller left ventricles with less depression of systolic function, as well as less aortic root and left atrial dilatation. Our data do not support the concept that the aortic valve should be replaced before the onset of symptoms to prevent irreversible LV damage in patients with isolated aortic stenosis.

Adult↗
PubMed1980

Verapamil therapy: a new approach to pharmacologic treatment of hypertrophic cardiomyopathy.

The hemodynamic and clinical effects of verapamil administration were examined in patients with hypertrophic cardiomyopathy. Infusion of 0.021 mg/kg/min of verapamil decreased the basal left ventricular outflow tract gradient from 94 +/- 14 to 49 +/- 14 mm Hg, while cardiac index increased from 2.5 +/- 0.2 to 2.8 +/- 0.2 L/min/sq m. Orally administered, 80 or 120 mg four times daily (QID), increased exercise capacity relative to placebo by 26% (1.6 +/- 0.5 minute; p less than 0.005) and propranolol, 40 or 80 mg QID, increased it by 21 +/- 8% (1.3 +/- 0.5 minute, p less than 0.025). Nine patients considered their symptomatic status "best" while receiving verapamil, seven while receiving placebo, and only three while receiving propranolol. Seventy-three patients have been discharged from the hospital receiving long-term verapamil therapy, and 49 have reported continuing symptomatic benefit with many showing improved exercise capacity up to two years later. Thus, verapamil can improve exercise capacity and symptomatic status in certain patients with hypertrophic cardiomyopathy, thereby providing physicians with a new therapeutic agent for the treatment of this disorder.

Adult↗
PubMed1980

Relative effects of nitroglycerin and nitroprusside during experimental acute myocardial ischemia.

When given during acute myocardial infarction (AMI), vasodilators such as nitroglycerin (TNG) and nitroprusside (NP) improve some of the hemodynamic determinants of myocardial oxygen demand. TNG has been shown to reduce ischemic injury during AMI, but variable results have been noted with NP therapy. To compare the effects of these two agents, 8 closed chest sedated dogs with pre-existing multi-vessel coronary constrictions underwent repeated, random-order, acute 15-min balloon occlusions of the left anterior descending coronary artery during the following conditions: (1) saline infusion (control), (2) TNG infusion, and (3) NP infusion. The severity of myocardial ischemia was estimated by summating the ST-segment elevations (xi ST) measured from 7 intramyocardial electrodes; mean left atrial pressure (LAP), heart rate (HR), and mean systemic arterial pressure (SAP) were also measured. No dog had left ventricular failure either before or after occlusion. Since HR and SAP responses to TNG and NP are different, the dogs were randomized into two subgroups: TNG and NP were infused in 4 dogs to produce similar increases in HR (10--20% greater than control), and in the other 4 to produce similar decreases in SAP (15--20% less than control). In each subgroup, xi ST was significantly lower following TNG than following NP. Moreover, in the total group of 8 dogs, xi ST after 10 min of occlusion averaged 38 +/- 10 mV during TNG treatment compared to 46 +/- 10 mV during control occlusion (P less than 0.05). In contrast, xi ST after 10 min of occlusion averaged 57 +/- 11 mV during NP treatment (P less than 0.01 compared to control occlusion). Thus, (1) when given to achieve similar hemodynamic changes following acute coronary occlusion, TNG reduced while NP increased myocardial ischemia, (2) although both 'vasodilators', TNG and NP appear to have different actions on various vascular beds, and (3) the hemodynamic changes induced by vasodilators do not in themselves provide an accurate index of directional alterations in myocardial ischemia.

Animals↗