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Biomedical subjects

K W Amon

Publications and source records attributed to K W Amon.

12 recordsLinked to original sources
PubMed1985

Long-term efficacy of high-dose diltiazem for chronic stable angina pectoris: 16-month serial studies with placebo controls.

In order to assess the long-term efficacy of diltiazem for the treatment of angina pectoris, eight patients with chronic stable exertional angina who were previously entered into a 4-month randomized, double-blind placebo controlled study, were studied for an additional 12-months. The patients continued to take diltiazem, 360 mg/day, and underwent treadmill exercise testing after 10 and 16 months of therapy. A single-blind placebo week was introduced after 16 months and a treadmill test was performed at the end of this week. Diltiazem therapy continued to augment exercise duration until 0.1 mV of ECG ST depression at 10 and 16 months as compared to the final placebo period: 573 +/- 133 (SD) seconds at 10 months; 565 +/- 148 seconds at 16 months; vs 431 +/- 151 seconds at final placebo (both p less than 0.001). Also, the time to angina pectoris was prolonged on diltiazem by 181 seconds at 16 months (p less than 0.01) and the total duration of exercise was increased by 101 seconds (p less than 0.001) as compared to placebo. In addition, angina frequency decreased from 17 +/- 11 attacks/week on placebo to 0.6 +/- 0.6 attacks/week during diltiazem therapy at 16 months. Two of the eight patients noted mild pedal edema, but no other adverse effects were experienced. Thus diltiazem, 360 mg/day, can be an effective single agent for the long-term treatment of chronic stable angina pectoris.

Aged↗
PubMed1984

Comparative value of 2-dimensional echocardiography and radionuclide angiography for quantitating changes in left ventricular performance during exercise limited by angina pectoris.

To compare left ventricular (LV) ejection fraction (EF) measurements made during exercise by 2-dimensional echocardiography (2-D echo) and gated equilibrium radionuclide angiography (RNA), 18 patients with angina pectoris were studied during graded upright bicycle ergometry. For RNA, the left anterior oblique view was used with the patient grasping the camera gantry during the 2-minute count acquisition required for EF calculation. For 2-D echo, biapical views were recorded with the patient's arms resting on a platform, and EF was calculated from volume measurements made using Simpson's rule. Exercise duration was similar for both studies, but EF at maximal exertion was higher by RNA than by 2-D echo (46 +/- 15% vs 35 +/- 15%, p less than 0.001). However, echo EF determined 1 minute before maximal exertion, which corresponded to the midpoint of the 2-minute count collection period for RNA, was similar to the RNA value at maximal exercise (44 +/- 12%). Analysis of individual EF values by 2-D echo at rest, at 1 minute before maximal exercise and at maximum exercise showed that there was little change in EF during submaximal exercise, but that EF decreased considerably at maximal exertion when the patients had angina pectoris. Therefore, when the time frame of data acquisition is considered, exercise 2-D echo and gated equilibrium RNA provide similar information regarding LVEF. The latter has the advantage of a 100% successful study frequency and the former is superior in its ability to detect the rapid changes in LV performance during exercise-limiting symptoms.

Aged↗
PubMed1984

Usefulness of the postexercise response of systolic blood pressure in the diagnosis of coronary artery disease.

The normal decline in systolic blood pressure (SBP) during the recovery phase of treadmill exercise does not occur in some patients with coronary artery disease (CAD). In others the recovery values of SBP exceed the peak exercise values. To examine the diagnostic value of this observation, we studied 31 normal subjects and 56 patients undergoing treadmill exercise before coronary cineangiography. Because of large differences in peak exercise pressures between the two groups, recovery ratios were derived by dividing the SBP at 1, 2, and 3 min after exercise by the peak exercise SBP. The 1, 2, and 3 min ratios in the normal subjects declined steadily from 0.85 +/- 0.07 (SD) to 0.79 +/- 0.06 and to 0.73 +/- 0.06, respectively, while the ratios in the patients with CAD remained elevated at 0.97 +/- 0.12 to 0.97 +/- 0.11 to 0.93 +/- 0.13. With use of the upper limits defined by two SDs of the normal value, recovery ratios were compared with the occurrence of angina and with ST segment depression on the exercise electrocardiogram in the patients with CAD. Abnormal ratios were more frequent in patients with CAD (53/56, 95%) than in those with ST segment depression (33/56, 59%), angina (37/56, 66%), and either ST segment depression or angina (42/56, 75%). Twenty of the patients with CAD who were on no medication underwent an additional treadmill exercise test on a separate day and no significant differences were found in the ratios from the two tests. Ten additional patients with CAD underwent treadmill exercise testing while on placebo and while on a beta-blocker.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1983

Exercise 2-dimensional echocardiography. Quantitation of left ventricular performance in patients with severe angina pectoris.

To assess the feasibility and reproducibility of exercise 2-dimensional (2-D) echocardiography for quantitating left ventricular size and performance, 25 patients with angina pectoris due to severe coronary artery disease and 10 normal subjects were studied before and after the administration of nitroglycerin. In 18 (72%) of the 25 patients, suitable biapical 2-D echocardiograms for quantitative analysis were recorded during upright bicycle exercise. Left ventricular volume (Simpson's rule), ejection fraction (EF), and wall motion score (10 segments graded 0 to 3, normal to dyskinetic) were measured at rest, and at peak exercise (control), 30 minutes later at rest, after nitroglycerin at rest, and at peak exercise. EF increased during control exercise in the normal subjects from 57 +/- 16 to 71 +/- 22% (p less than 0.01), but was unchanged in the patients during exercise before nitroglycerin. In 7 patients (39%), marked increases in EF (greater than 0.05 units) during exercise occurred after nitroglycerin administration. The wall motion score increased significantly in the patients during control exercise, from 2.6 +/- 3.4 to 5.6 +/- 4.5, but was less at maximal exercise after nitroglycerin (3.4 +/- 4.0, p less than 0.001). Intra- and interobserver variability in these measurements was acceptable. Thus, quantitation of left ventricular performance during exercise by biapical 2-D echocardiography can be accomplished in a high proportion of patients with coronary artery disease (CAD) and can be used to assess the effects of therapeutic interventions.

Adult↗
PubMed1983

Effect of the undisturbed pericardium on left ventricular size and performance during acute volume loading.

Studies in instrumental dogs have suggested that the pericardium alters left ventricular diastolic pressure-volume relations and thus may influence systolic performance. However, the instrumentation used in these studies disrupts the pericardium and may have influenced the results. We therefore studied five conscious dogs by methods not traumatic to the pericardium, before and after pericardiectomy. Although heart rate and left ventricular systolic and end-diastolic pressures were not different before or after pericardiectomy, either at rest or during volume loading, end-diastolic volume measured by biplane two-dimensional echocardiography increased post pericardiectomy at rest from 38 +/- 4 (SE) to 61 +/- 4 ml (p less than 0.05) and during volume loading from 68 +/- 5 to 79 +/- 5 ml (p less than 0.005). After pericardiectomy, ejection fraction was unchanged, but the peak value of the first derivative of left ventricular systolic pressure (dP/dt) increased significantly at rest from 17 +/- 2 to 26 +/- 4.0 x 10(2) mm Hg/sec. We conclude that pericardiectomy shifts the left ventricular end-diastolic pressure-volume curve to the right and increases the systolic isovolumic index of dP/dt in the basal state.

Animals↗
PubMed1982

Effect of nitrate on determinants of myocardial oxygen consumption during exercise.

We evaluated the effects of isosorbide dinitrate on some of the major determinants of myocardial oxygen demand during upright exercise in ten normal subjects. In addition to heart rate and systolic blood pressure, we assessed left ventricular size and performance by echocardiography. Compared to the control study, heart rate was significantly faster after the nitrate administration at rest (67 +/- 14 versus 83 +/- 21 beats/minute), but there was no difference in heart rate at any stage during exercise. Systolic blood pressure also was significantly lower at rest after nitrate (104 +/- 8 versus 92 +/- 2 mm Hg) but was similar to control after 6 minutes of exercise. Echocardiographic end-diastolic dimension was decreased at rest post-nitrate (45.3 +/- 4.7 versus 40.2 +/- 4.2 mm) and remained significantly reduced during exercise by an analysis of variance. We conclude that a major beneficial effect of nitrates on myocardial oxygen demand during upright exercise is a decrease in left ventricular size which reduces wall tension.

Adult↗
PubMed1982

Hemodynamic effects of N-acetylprocainamide in heart disease.

In six normal subjects and 6 patients with primary cardiomyopathy, left ventricular performance was evaluated at rest and during isometric handgrip exercise after 4 days of oral N-acetylprocainamide (NAPA) at each of the three dosage levels (3, 4, 5, and 6 gm/day). Changes in heart rate, blood pressure, and echocardiographic performance indices were noted during isometric exercise, but no effect of NAPA could be demonstrated. In five additional patients with ventricular dysrhythmias due to cardiac diseases, NAPA was given by vein until dysrhythmias were controlled and then a maintenance infusion was continued for 48 hr. Continuous ECG recordings showed excellent dysrhythmia control in four of the five patients, but no effect of NAPA on heart rate, blood pressure, mean pulmonary artery pressure, mean pulmonary artery wedge pressure, or cardiac output was demonstrated, either at the peak of initial infusion (serm NAPA 27 +/- 6.7 microgramsm/ml) or at steady state during the maintenance infusion (16 +/- 4.5 microgramm/ml). We conclude that NAPA by vein and mouth in clinically appropriate doses should be safe in patients with the reduced left ventricular performance due to cardiac disease.

Acecainide↗
PubMed1979

Upright exercise echocardiography.

A simple technique for obtaining high-quality echocardiograms of the left ventricle during upright bicycle exercise is described. The use of this method has resulted in left ventricular dimension data that are consistent with the results of studies in conscious, previously instrumented dogs during running. Careful subject selection is important, however, as only 1 of 5 normal subjects was found suitable for these studies. Therefore, we believe that upright exercise echocardiography is feasible in selected subjects and provides useful physiologic information about left ventricular performance during exercise.

Adolescent↗
PubMed1976

Favorable effects of oral maintenance digoxin therapy on left ventricular performance in normal subjects: echocardiographic study.

Left ventricular performance was assessed with echocardiography in 10 normal subjects before and during maintenance therapy with digoxin (0.5 mg/day orally) in the basal state and after acute pressure loading with intravenously administered phenylephrine. During digoxin therapy, despite a decrease in mean heart rate of 5 beats/min in the basal state, mean left ventricular ejection fraction increased from 74 +/- 2 to 79 +/- 1 percent (standard error, P less than 0.03); percent shortening of a left ventricular minor dimension increased from 37 +/- 2 to 41 +/- 1 percent (P less than 0.04) and the mean rate of left ventricular dimension shortening increased from 5.66 +/- 0.22 to 6.31 +/- 0.23 cm/sec (P = 0.05). During acute pressure loading with phenylephrine there was no change in mean heart rate after digoxin and mean ejection fraction increased from 69 +/- 3 to 75 +/- 2 percent; mean percent shortening increased from 33 +/- 2 to 38 +/- 2 percent; mean rate of shortening increased from 5.46 +/- 0.32 to 6.48 +/- 0.33 cm/sec and mean normalized rate of shortening increased from 1.11 +/- 0.06 to 1.29 +/- 0.05 sec-1 (all P less than 0.01). In a few subjects the response to digoxin did not coincide with the mean data for the whole group. This variability was largely due to difficulties in exactly matching heart rate between the control and digoxin studies. These data (1) support the concept that long-term oral digoxin therapy exerts a positive inotropic effect on the normal left ventricle, and (2) demonstrate the usefulness of echocardiography in nonivasive assessment of the effects of drugs on left ventricular performance.

Adult↗
PubMedDate not supplied

Improved two-dimensional echocardiographic technique for left ventricular aneurysm detection.

In order to determine the sensitivity and reproducibility of a new two-dimensional echocardiographic technique for detecting left ventricular aneurysms, 16 patients suspected of having aneurysms were evaluated prospectively. Left ventricular angiography demonstrated aneurysms in 15 of the 16 patients. All 15 were detected by two-dimensional echocardiography but three were identified only in a view rotated 45 degrees clockwise from the apical four-chamber view. The analysis of 16 wall segments for each patient showed excellent agreement between two observers. Therefore, two-dimensional echocardiography, utilizing four apical views 45 degrees apart, is reliable and reproducible for the detection of left ventricular aneurysms.

Angiography↗