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Biomedical subjects

D R Redwood

Publications and source records attributed to D R Redwood.

At least 19 recordsLinked to original sources
PubMed1990

Major complications of coronary arteriography: the place of cardiac surgery.

The records of the catheter laboratory at St George's Hospital between 1983-1988 were reviewed to determine how often emergency coronary bypass surgery was performed because of a complication arising during elective coronary arteriography. A total of 11,216 cardiac procedures were performed; 5781 were confined to left ventricular angiography and coronary arteriography in patients with suspected coronary artery disease. Fourteen patients, whose investigation had been considered routine, suffered profound circulatory collapse during the procedure. Emergency cardiac surgery was undertaken in 13, with long term survival in 10. This experience suggests that, even in patients considered to be at low risk, there were major complications requiring emergency coronary surgery in at least 2.4 per 1000 coronary arteriograms performed. Survival after emergency cardiac surgery in these patients was 77%. These findings and the access to cardiac surgery should be considered when the development of facilities for cardiac catheterisation is planned.

Adult↗
PubMed1979

Exercise performance after septal myotomy and myectomy in patients with obstructive hypertrophic cardiomyopathy.

The effect of left ventriculomyotomy and myectomy on exercise capacity and cardiac function in patients with obstructive hypertrophic cardiomyopathy has not previously been determined. In this study, 29 patients were evaluated during graded treadmill exercise before and after operation. Postoperatively, 27 of 29 patients reported symptomatic improvement and had greatly reduced left ventricular outflow gradient. Twenty-five of 28 patients (89 percent) attained higher exercise levels after operation, and this was accompanied by an increase in total body oxygen consumption from 16 to 21 ml/min per kg (P less than 0.005). A significant increase in cardiac index during maximal exercise also accompanied this improved exercise performance (5.0 to 5.7 liters/min per m2, P less than 0.05). The increase in maximal cardiac index was associated with greater desaturation of mixed venous blood (34 to 24 percent, P less than 0.02) in patients with preoperative angina. At a given level of mixed venous oxygen saturation (30 percent), overall mean cardiac index was higher postoperatively (4.6 to 5.2 liters/min per m2, P less than 0.05). These results suggest that, although several mechanisms probably contribute to symptomatic improvement after myotomy and myectomy, enhanced cardiac performance plays an important role in the majority of patients.

Adolescent↗
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

Abnormal right ventricular size and ventricular septal motion after atrial septal defect closure: etiology and functional significance.

Postoperative echocardiogram often demonstrate persistent right ventricular dilatation and paradoxic ventricular septal motion after repair of an atrial septal defect. To determine the prevalence, causes and significance of these echocardiographic abnormalities, 31 patients were studied with catheterization and echocardiography before and after repair of an atrial septal defect. Before operation, every patient manifested right ventricular dilatation, and all but one had abnormal septal motion. After operation, right ventricular dilatation was noted in 24 (77%) and abnormal septal motion in 21 (68%) patients despite the absence of residual left to right shunting in 30 (97%). These echocardiographic abnormalities could be correlated with age at operation and length of postoperative follow-up study but did not correlate with the degree of preoperative right ventricular enlargement or with shunt size or right ventricular pressure before or after operation. There was no associated functional deficit as demonstrated by the normal maximal oxygen consumption in all 13 patients who underwent treadmill exercise testing 5 to 38 months after operation; these patients included 9 with persistent right ventricular enlargement and abnormal septal motion.

Adolescent↗
PubMed1978

Nitroglycerin-induced improvement in exercise tolerance and hemodynamics in patients with chronic rheumatic heart valve disease.

Nitroglycerin reduces elevated left ventricular filling and pulmonary arterial pressures in resting patients with rheumatic valve disease and reduces symptoms when given over long periods to patients with primary myocardial disease. To determine whether nitroglycerin may prove effective therapeutically in ambulatory patients with heart valve disease, its effects on hemodynamics and exercise capacity were studied in 11 severely symptomatic adults who were already receiving optimal treatment with digitalis and diuretic agents. Seven had predominant mitral valve disease, one had predominant aortic insufficiency and three had equally severe mitral and aortic valve disease. Maximal exercise capacity was assessed with graded treadmill exercise after placebo and after nitroglycerin (0.5 mg sublingually) administered in random sequence to each patient. Exercise capacity (exercise time to limiting fatigue or dyspnea) increased from a mean of 8.3 minutes after placebo to 9.8 minutes after nitroglycerin (P less than 0.005). Eight patients were studied hemodynamically during further intense treadmill exercise. Pulmonary arterial pressure was significantly lower (P less than 0.05) after nitroglycerin than after placebo (mean 44 versus 56 mm Hg), but cardiac output was greater after nitroglycerin (5.0 versus 4.6 liters/min, P less than 0.005). Thus, nitroglycerin appears to increase exericse tolerance and improve the hemodynamic response to exercise in patients with heart valve disease and may be valuable in the long-term pharmacologic therapy of such patients.

Administration, Oral↗
PubMed1977

Aortic valve replacement in the elderly. Encouraging postoperative clinical and hemodynamic results.

Seventy-three patients aged 60 and over and 277 patients under 60 years of age underwent isolated aortic valve replacement (AVR) for aortic stenosis, regurgitation, and mixed disease from 1966 through 1975. Cardiac catheterization was performed five to nine months following operation in 77% of these patients. Follow-up averaged 55 months per patient. The hospital mortality in the elderly group was 2.7%, compared to 5.8% in the younger group. The late cardiac mortality was 21% and 19%, respectively. There was significant improvement (P less than .001) in the left ventricular end-diastolic pressure, cardiac index, and functional class in each of the three disease groups in the younger as well as the elderly patients. More important, the magnitude of improvement in each of these variables in patients over and under 60 years of age was not significantly different. Increasing longevity will make cardiac operations more common in the older population. These findings indicate that AVR carries the same low risk and brings about a similar improvement in left ventricular pump function in patients older and younger than 60.

Aged↗
PubMed1977

Prevalence and characteristics of disproportionate ventricular septal thickening in patients with acquired or congenital heart diseases: echocardiographic and morphologic findings.

Echocardiographic and necropsy studies were performed in 304 patients with various cardiac diseases. The overall prevalence of disproportionate ventricular septal thickening (septal to free wall ratio greater than or equal to 1.3) was 10%. However, it was related to the type of cardiac lesion. Prevalence was high (greater than 20%) in pulmonary stenosis or primary pulmonary hypertension, lower (less than 15%) in Eisenmenger syndrome or aortic or mitral valvular disease and was not present in atrial or ventricular septal defect. In right ventricular overload, prevalence of disproportionate septal thickening correlated with increasing ventricular systolic pressure. None of 16 patients with disproportionate septal thickening studied at necropsy showed marked disorientation of cardiac muscle cells in the ventricular septum, characteristic of genetically transmitted asymmetric septal hypertrophy (ASH). Furthermore, disproportionate septal thickening was demonstrated by echocardiography in only one of 59 first degree relatives of patients with disproportionate septal thickening and associated cardiac diseases. Thus, disproportionate ventricular septal thickening associated with other cardiac diseases usually is due to secondary hypertrophy and is not a manifestation of genetically transmitted ASH.

Adolescent↗
PubMed1977

ECG-gated scintillation probe measurement of left ventricular function.

A nonimaging, ECG-gated scintillation-probe system is described that permits real-time quantification, at high temporal resolution, of the time variation of left ventricular (LV) volume over a complete, average cardiac cycle. Linearity between counting rate and volume, probe positioning, and background correction were investigated for both cylindrically collimated (CC) and parallel-hole-collimated (PC) detectors. In 53 patient studies, results obtained with these probes were compared with results obtained from an ECG-gated gamma camera system (CS) with high temporal resolution. Time-activity curves obtained by all three devices were essentially identical in shape (for CC against CS, r=0.93; for PC against CS, r=0.98) and in intracycle timing. Left-ventricular ejection fractions obtained with the probes showed workable agreement with the camera; for CC against CS, r=0.85 (N=31; for PC against CS, r=0.90 (N=21). When LV background is removed as a source of error, the correlation between (PC) probe and camera is improved (r=0.95, N=21). This suggests that the portable probe system be used in circumstances where exact knowledge of LV background is minimally important--e.g., continuous bedside monitoring of changes in LV function.

Adult↗
PubMed1977

Clinical and hemodynamic results following triple valve replacement: mechanical vs porcine xenograft prostheses.

This study summarizes the results in 26 patients of triple valve replacement (TVR) performed between 1967-1975. The first ten patients (group I) received all-mechanical valves, but the last 16 (group II) received porcine xenograft atrioventricular and porcine or mechanical aortic valves. Preoperatively, all patients were functional class II or IV with pulmonary arterial and venous hypertension. Early mortality was 30% group I and 18.8% group II; late mortality has been 30% group I and 6.3% group II. Total operative and bypass time, and duration of postoperative respiratory support was less (P less than 0.025) in group II than in group I. Postoperative catheterization performed in 16 of 26 patients demonstrated significant reduction (P less than 0.05) in pulmonary arterial and venous hypertension, and aortic and mitral gradients in group II. There have been no late complications or valve malfunctions in group II. An improvement of at least two functional classes was seen in 4/6 group I and 12/13 group II operative survivors. The results of TVR with porcine xenografts compare favorably with those of all-mechanical replacements and deserve further evaluation.

Adult↗
PubMed1976

Asymetric septal hypertrophy in childhood.

Although considerable information is available concerning the clinical features and natural history of asymmetric septal hypertrophy (ASH) in adults, little is known of this disease in children. The clinical characteristics and course of 46 children with ASH, who were evaluated at the National Heart and Lung Institute, have been analyzed. Twenty-four children had obstruction to ventricular outflow; 22 children had no obstruction to ventricular outflow, including 11 patients without overt manifestations of cardiac disease other than echocardiographic evidence of ASH. Thirty-five of the 46 children have been followed for one to 16 years (average 7.4 years). These latter children represent that subgroup of patients with ASH referred to the National Heart and Lung Institute and diagnosed prior to the general availability of echocardiography. The clinical course of these patients was variable. Fourteen (40%) of the 35 patients improved or remained stable, including four patients who received propranolol. Ten (29%) of the 35 patients deteriorated clinically and 11 (31%) of the 35 patients died suddenly (4% mortality per year). Two of the patients who died suddenly had previously undergone operation (six and 13 years previously) with resultant abolition of the outflow gradient; four others were taking propranolol. Neither symptomatology, electrocardiographic abnormalities, heart size, left ventricular ejection or upstroke time, magnitude of outflow gradient, or left ventricular end-diastolic pressure proved predictive of sudden death. Excluding patients who had previous operation, eight (40%) of 20 patients with obstruction who were followed long term and one (9%) of 11 patients without outflow obstruction died suddenly. Thus, the clinical and hemodynamic spectrum of ASH in childhood is broad. However, deterioration in clinical condition or sudden death has been relatively common in children with overt signs of cardiac disease.

Adolescent↗
PubMed1976

Relation between echocardiographically determined left atrial size and atrial fibrillation.

In an attempt to define quantitatively the relation between left atrial size and atrial fibrillation, echocardiography was used to study 85 patients with isolated mitral valve disease, 50 patients with isolated aortic valve disease, and 130 patients with asymmetric septal hypertrophy. In all three groups of patients, atrial fibrillation was rare when left atrial dimension was below 44 mm (3 of 117 or 3%) but common when this dimension exceeded 40 mm (80 of 148 or 54%). In addition, when left atrial dimension exceeds 45 mm, cardioversion, while initially successful, is unlikely to produce sinus rhythm that can be maintained at least six months. These data suggest that left atrial size is an important factor in the development of atrial fibrillation and in determining the long term result of cardioversion. The pathophysiologic mechansim most consistent with this is that a chronic hemodynamic burden initially produces left atrial enlargement which in turn predisposes to atrial fibrillation. Only prospective studies will determine definitively whether these observations will be useful in decisions concerning prophylactic anticoagulation and elective cardioversion.

Adolescent↗
PubMed1976

Tunnel subaortic stenosis: left ventricular outflow tract obstruction produced by fibromuscular tubular narrowing.

The clinical and morphologic features of tunnel subaortic stenosis, an unusual form of obstruction to left ventricular outflow, are described in 11 patients. Although patients with tunnel subaortic stenosis demonstrate a variety of cardiovascular malformations, the most characteristic anatomic feature is fibromuscular tubular narrowing of the outflow tract that remains relatively unchanged during the cardiac cycle. The aortic anulus was abnormally small in six of the 11 patients, including one who also had a hypoplastic ascending aorta. Evidence of a small mitral orifice was present in two patients, and two other patients had asymmetric septal hypertrophy. Although operation was successful in significantly reducing the outflow gradient in two of the seven operated patients, all seven patients had gradients of 50 mm Hg or more at the most recent postoperative evaluation. Three patients (two with previous operation) died suddenly; each of these patients had mild or no symptoms. Because of the apparent ineffectiveness of current operative methods in patients with tunnel subaortic stenosis, it is important to differentiate this condition from obstructions to left ventricular outflow.

Adolescent↗
PubMed1976

Protection of ischemic myocardium by nitroglycerin: experimental and clinical results.

Nitroglycerin (NTG) traditionally has bben avoided in the treatment of pain caused by acute myocardial infarction because of the belief that NTG-induced decrease in arterial pressure and concomitant reflex increase in heart rate might extend the ischemic process. However, recent experimental and clinical investigations cast doubt on this concept. For example, when the left anterior descending coronary artery is acutely occluded in normal dogs or in dogs when chronic coronary occlusions and extensive collaterals, NTG reduces ST-segment evevation (and presumably myocardial ischemia). This salutary effect occurs despite lowering of systemic arterial pressure, as long as excessive reflex tachycardia does not result; the magnitude of ischemia reduction is potentiated when methoxamine or phenylephrine are administered simultaneously to abolish the NTG -induced hypotension and reflex tachycardia. NTG and methoxamine treatment also results in 1) reduction of infarct size as (as assessed by gross morphologic examinations and myocardial CPK levels) in dogs subjected to 5 hours of coronary occlusion, and 2) increase in ventricular fibrillation (VF) threshold and reduction of the incidence of spontaneously occurring VF in dogs with acute coronary occlusion. Finally, the effectiveness of NTG during acute myocardial iinfarction (AMI) in man has been studied. Multiple precordial electrodes were used to measure changes in the degree of ST-segment elevation; these changes were used as an index of alterations in myocardial ischemic injury. Patients with normal pulmonary capillary wedge pressures ( less than 15 mm Hg) did not benefit consistently from NTG alone; however, when phenylephrine was administered with NTG (to abolish NTG-induced arterial pressure reduction and reflex increase in heart rate), ST-segment elevation diminished consistently. In patients with elevated wedge pressures ( greater than 15 mm Hg), NTG alone consistently reduced ischemia; addition of phenylephrine often partially reversed this benefit. Thus, administration of NTG, alone or with phenylephrine, appears to reduce myocardial ischemic injury during AMI in man; however, the response to phenylephrine depends upon the presence or absence of LV failure prior to treatment. These experimental and clinical results suggest this form of therapy may be use in reducing infarct size in man, although additional studies are necessary to determine the functional significance of these acute electrophysiologic alterations.

Animals↗
PubMed1975

Reduction in myocardial ischemia with nitroglycerin or nitroglycerin plus phenylephrine administered during acute myocardial infarction.

Nitroglycerin reduces ischemic injury during acute myocardial infarction (AMI) in dogs--an effect that is potentiated when drug-induced hypotension and tachycardia are prevented with phenylephrine. To determine the effectiveness of nitroglycerin, alone or with phenylephrine, during AMI in man, 12 patients (five or whom had left heart failure) were evaluated by summing ST-segment abnormalities (sigmaST) from 35 precordial electrodes. The seven patients without heart failure did not benefit consistently from nitroglycerin alone; however, addition of phenylephrine to abolish nitroglycerin-induced arterial pressure reduction uniformly diminished sigmaST (4.9 to 3.2 mv; P less than 0.05). In patients with heart failure, nitroglycerin alone consistently reduced ischemia (5.8 to 4.4 mv, P less than 0.05); addition of phenylephrine often partially reversed this effect. Thus, administration of nitroglycerin, alone or with phenylephrine, can reduce myocardial ischemic injury during AMI in man; however, the response to phenylephrine depends on the presence or absence of left ventricular failure before treatment.

Acute Disease↗