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Biomedical subjects

R A DeSilva

Publications and source records attributed to R A DeSilva.

At least 19 recordsLinked to original sources
PubMed1998

Late neurocognitive changes from neurological damage following coronary bypass surgery.

A detailed case study with neuropsychological data over a 26-year period was used to explore the relationship between neurocognitive vulnerability preoperatively and subsequent neurocognitive decline identified several years postoperatively. Guidelines regarding the importance of neuropsychological assessment of intelligence, attention, memory, language, and visual-spatial planning and organizational skills are provided. Such evaluations clarify postoperative treatment planning because rehabilitation of cardiac patients with premorbid neurocognitive deficits poses special rehabilitation problems. With a detailed neurologic history as part of the preoperative evaluation, healthcare providers can identify acute and subtle risk factors for postoperative neurologic syndromes. This may lead to interventions designed to provide increased patient and family support.

Aged↗
PubMed1997

George Ralph Mines, ventricular fibrillation and the discovery of the vulnerable period.

The discovery of the vulnerable period of the ventricle unmasked one of the major electrical properties of the heart. Since its description by George Ralph Mines in 1914, it has become a crucial concept in understanding the electrophysiologic basis for ventricular fibrillation. Mines also proposed the theoretical basis for the occurrence of reentrant arrhythmias. Although these concepts are widely known, Mines himself remains an obscure figure since his own sudden death at a young age. Mines was a talented researcher who had a short but prolific career in electrophysiology. The historical importance of his work lies in the influence he had on our understanding and treatment of cardiac arrhythmias as well as in the experimental methods he developed, which inspired a new era of quantitative thinking in electrophysiology.

Canada↗
PubMed1993

Preliminary screening of the relationship of serum lipids to survival of chronic dialysis patients.

To assess the predictive value of serum lipid measurements in dialysis patients once the initial decrease on early dialysis had occurred, we obtained random serum cholesterol and triglyceride levels in stable, chronic dialysis patients who were then followed up to 9 years. Derived LDL (DLDL) was estimated by the Friedewald formula, calculated for all HDL levels between 30 and 45 mg/dL, and evaluated statistically against a panel of vascular disease markers, including clinical assessment for coronary, peripheral, and cerebrovascular disease; ECG, both standard and ambulatory; two-dimensional echocardiogram; and medications. Survival was calculated from entry (not dialysis onset) for 58 hemodialysis and 33 peritoneal dialysis patients. The 91 patients (49 males, 74 diabetics) were divided by cholesterol level (> or = 175 mg/dL = 53, < 175 = 38), triglyceride (> or = 175 mg/dL = 55, < 175 = 36), and DLDL (> or = 75 = 58, < 75 = 24). High total cholesterol was present in a larger proportion of females than low cholesterol, but groups were not different with respect to all vascular determinants, including survival (mean = 33.4 months vs. 43.2, p = NS). High vs. low triglyceride groups were not different with respect to vascular indicators, except for both incidence of abnormal standard ECG (69% vs. 42%, p < 0.05) and survivals (mean = 42.0 vs. 30.7, p < 0.05; 1 year = 80% vs. 56%, p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1992

Usefulness of left ventricular size and function in predicting survival in chronic dialysis patients with diabetes mellitus.

To identify patients at high risk for sudden death, a group of stable patients on maintenance dialysis with diabetes mellitus were studied for up to 135 months to determine if there were clinical, laboratory or echocardiographic predictors of high risk. Eighty-two patients on maintenance dialysis who underwent clinical, laboratory evaluation and echocardiography were enrolled and followed for a mean of 25 months for cardiac and noncardiac complications. Thirty-seven patients with normal wall motion and left ventricular (LV) internal diameter had a mean survival of 35.8 months; 28 patients survived greater than 12 months. Seven patients with normal LV wall motion and dilated LV cavities had a mean survival of 45.7 months; 7 patients survived greater than 12 months. Fifteen patients with abnormal LV wall motion and normal internal LV dimensions had a mean survival of 17 months; 7 patients survived greater than 12 months. Twenty-three patients with both abnormal LV wall motion and dilated LV cavities had a mean survival of 7.8 months; 5 patients survived greater than 12 months. Although echocardiographic abnormalities predicted cardiac mortality at 6 and 12 months, the combination of an abnormal standard electrocardiogram at baseline, clinical history of angina pectoris, and prior documented myocardial infarction or congestive heart failure did not. When the study group was divided by mode or duration of dialysis, presence or absence of diabetes, or use of cardioactive drugs, echocardiographic LV wall motion abnormalities remained the most important determinant of survival.

Adult↗
PubMed1992

Pathophysiology and triggers of acute myocardial infarction: clinical implications.

A new approach to identification of the triggering mechanisms of acute myocardial infarction has been provided by the observation that the disease occurs more frequently during the morning hours compared to other times of day. This circadian variation results primarily from an increased relative risk during the initial 2-3 h after awakening and arising. The precise relationship between the onset of myocardial infarction and external factors such as activity and meal patterns needs to be determined in controlled epidemiologic studies. The possible underlying pathophysiologic mechanisms responsible for the circadian pattern of myocardial infarction include acute variations of blood pressure, heart rate, platelet aggregability and fibrinolytic activity, leading to an increased risk of plaque rupture and intracoronary thrombosis. Clinical implications of these findings include the need to design preventive regimens to provide maximum protection at the time of peak risk of myocardial infarction.

Adrenergic beta-Antagonists↗
PubMed1990

Cardiac conduction defects associated with aortic and mitral valve calcification in dialysis patients.

The prevalence of aortic valve and mitral valve or mitral annular calcification by echocardiography was studied in 66 dialysis patients and correlated with results of 24-h ambulatory and resting ECG data and 12-month survival. The well-known association of mitral valve or mitral annular calcification with cardiac conduction defects was confirmed. Those patients with mitral valve or mitral annular calcification demonstrated a higher prevalence of first-degree atrioventricular block and bundle branch block. Despite advanced age and these conduction defects, those patients with mitral valvular calcification did not show decreased survival at 12 months.

Aortic Valve↗
PubMed1983

Unrecognized organic mental disorders in survivors of cardiac arrest.

Long-term survivors of cardiac arrest may suffer from mild cerebral impairment manifested primarily by personality changes and behavioral symptoms that can be mistaken for emotional responses to illness. The authors report six cases that illustrate the clinical problem of differentiating depression from organic brain dysfunction in this population. The diagnosis is facilitated by observation over time and by information from the spouse on baseline and current function. Chronicity, dysinhibition, apathy, and disturbances of judgment and insight indicate cerebral dysfunction. The accurate diagnosis of cerebral impairment after cardiac arrest is essential to the rehabilitation process.

Adult↗
PubMed1981

Lignocaine prophylaxis in acute myocardial infarction: an evaluation of randomised trials.

Although lignocaine has been used in coronary care units for almost two decades, its role in preventing ventricular fibrillation (VF) during acute myocardial infarction (MI) is still debated. Of fifteen randomised trials of lignocaine prophylaxis, most showed no apparent benefit. When the data from all fifteen trials were pooled and a summary relative risk estimate calculated, there was a significant benefit of lignocaine treatment in preventing VF. However, the trials had widely differing treatment schedules, modes of drug administration, and doses of lignocaine; to decrease the clinical heterogenity, minimum criteria for adequacy of treatment were established and the data from six trials which fulfilled these requirements were pooled. The summary relative risk estimate calculated from the pooled data of these six trials also demonstrated a significant prophylactic effect of lignocaine that was even greater when the two trials which treated patients with left ventricular failure and shock were excluded. From these analyses, it is concluded that lignocaine treatment provides prophylaxis against VF in acute MI. The failure of most trials to demonstrate such a prophylactic effect is due to small sample sizes and inadequate treatment protocols.

Clinical Trials as Topic↗
PubMed1981

Acute psychological disturbances preceding life-threatening ventricular arrhythmias.

To investigate the prevalence of acute psychological disturbances during the 24 hours preceding life-threatening ventricular arrhythmias, we studied the mental states and psychological experiences preceding arrhythmic episodes in 117 patients who were referred for antiarrhythmic management. Sixty-two had survived cardiac arrest and 55 suffered symptomatic ventricular tachycardia. Twenty-five patients were experiencing acute emotional disturbances during the 24 hours preceding the arrhythmias. Eighteen had two or more episodes associated with psychological disturbances. These 25 patients were distinguished from the rest of the series in having generally less severe structural heart disease.

Acute Disease↗
PubMed1981

Tyrosine administration decreases vulnerability to ventricular fibrillation in the normal canine heart.

Intravenous infusion of tyrosine (1, 2, or 4 milligrams per kilogram) for 20 to 30 minutes caused dose-dependent increases in the ventricular fibrillation threshold in normal dogs. Administration of valine, a neutral amino acid that competes with tyrosine for uptake at the blood-brain barrier, in a dose equimolar to the most effective dose of tyrosine, slightly decreased the ventricular fibrillation threshold when given alone and significantly blocked elevation of the ventricular fibrillation threshold after tyrosine infusion. Hence, tyrosine, presumably acting in the central nervous system, can protect against certain ventricular arrhythmias.

Animals↗
PubMed1980

Cardioversion and defibrillation.

The use of electrical energy for the immediate treatment of atrial and ventricular arrhythmias is practical and easily applied. The method, though simple, is the most effective method for terminating cardiac arrhythmias and is associated with only a low risk if properly employed. In symptomatic patients, the utilization of cardioversion reduces patient discomfort and complications which may occur while awaiting pharmacologic reversion of arrhythmia. At present, transthoracic defibrillation is the only practical method for terminating VF. Despite the safety of electrical reversion, proper precautions are necessary to prevent complications. In particular, the discharge of excessive energies, especially in the presence of digitalis toxicity, promises grave and life-threatening consequences. The use of antiarrhythmic medications is not supplanted by cardioversion and defibrillation. Rather, ongoing drug therapy is frequently necessary to prevent recurrence of arrhythmia.

Animals↗
PubMed1980

Episodic drug treatment in the management of paroxysmal arrhythmias.

The use of maintenance medication in the treatment of episodic cardiac arrhythmia is often complicated by problems of patient compliance with therapy and adverse side effects. Furthermore, repeated hospitalizations and cardioversions are both costly and inconvenient. A method of intermittent drug therapy is described in which antiarrhythmic medication is taken only at the onset of an episode of arrhythmia. This approach was effective in terminating both supraventricular and ventricular arrhythmias in 24 of 32 patients and obviated the need for hospitalization and further treatment. In cases in which maintenance therapy was required because of the frequent occurrence of arrhythmia, periodic drug therapy was still of value in the treatment of breakthrough episodes. The use of intermittent drug therapy is a safe and effective approach to the management of episodic cardiac arrhythmia and, in addition, results in significant financial saving.

Adolescent↗
PubMed1980

Psychophysiologic factors in sudden cardiac death.

Sudden cardiac death due to ventricular fibrillation is the leading cause of fatality in the industrially developed world. A considerable body of evidence indicates that the higher nervous system modifies electrical activity of the heart and may trigger sudden death. The evidence for increased risk for ventricular fibrillation due to psychophysiologic factors is supported predominantly by animal studies, but increasing evidence is forthcoming from human studies. The involvement of psychiatrists, psychologists, and cardiologists in a multidisciplinary approach to managing patients at risk for sudden death from ventricular fibrillation is yielding significant insights and prolonging their lives.

Animals↗