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Biomedical subjects

C T Peter

Publications and source records attributed to C T Peter.

35 records · Page 2Linked to original sources
PubMed1991

Syncope: evaluation and management. A review of current approaches to this multifaceted and complex clinical problem.

Syncope is a common but complex medical disorder with a multitude of etiologies, some of which are still not well understood. In a general population, the greatest diagnostic yield is from the history and physical examination. Numerous other diagnostic modalities include Holter monitoring, signal-averaged ECG, cardiac electrophysiology study, and tilt table testing. A defined etiology will not be determined for a large percentage of patients after such an extensive work-up. Management of patients is based on the cause of syncope and is difficult in those patients in whom an etiology cannot be established. The syndrome of neurally mediated syncope is a relatively recently appreciated entity and provides important clinical investigational challenges.

Electrocardiography↗
PubMed1991

Sudden death. Evaluation and prevention.

The clinical approach to sudden death involves the assessment of risk in a heterogeneous group of patients via a combination of modalities, both invasive and noninvasive. These include Holter monitoring, assessment of left ventricular ejection fraction, signal-averaged high gain ECG, and cardiac electrophysiology study. The management of these patients requires a better understanding of the underlying pathophysiology and clinical factors in the individual patient and is based on an approach using antiarrhythmic agents, surgery, catheter ablation techniques, and the AICD. The current trend appears to be more toward nonpharmacologic methods, especially the use of devices.

Anti-Arrhythmia Agents↗
PubMed1990

The use of signal-averaged electrocardiography in predicting patients at high risk for sudden death.

Delayed and inhomogeneous ventricular depolarization is found in patients with ventricular tachycardia. This abnormal activity may be discerned as a ventricular late potential (LP) by applying special signal-averaging techniques to the surface electrocardiogram. The presence of LPs after acute myocardial infarction (AMI) is associated with an increased risk of serious ventricular arrhythmias and sudden cardiac death during the subsequent year. Thus the signal-averaged ECG (SAECG) can identify a high risk subset of patients following AMI for whom more intensive diagnostic and/or therapeutic measures are indicated. Patients with findings ordinarily indicative of a relatively poor prognosis, such as reduced left ventricular ejection fraction, may be more precisely classified into high or low risk based on the presence or absence of LPs. The SAECG may be helpful in selecting patients with other types of presentations, such as syncope, who are likely to benefit from electrophysiological testing.

Cardiac Pacing, Artificial↗
PubMed1980

The effect of long-term diphenylhydantoin therapy on glucose tolerance and insulin secretion: a controlled trial.

The influence of long-term administration of diphenylhydantoin (DPH) on glucose tolerance and insulin secretion was studied in a random controlled trial in non-epileptic patients receiving the drug for 2 years following recovery from myocardial infarction. While receiving DPH, insulin response to glucose was less than that in the control group, both in absolute terms and when related to the blood glucose level. Despite this, glucose tolerance did not differ from the control group. One month after cessation of DPH, the plasma insulin response had returned to the levels found in the control group, and glucose tolerance had improved to be significantly better than that found in the control group. Thus, the tendency of DPH to impair the insulin response to glucose has been confirmed in this controlled study. However, this does not result in significantly impaired glucose tolerance; it is suggested that the decreased insulin secretion is accompanied by improved insulin sensitivity.

Blood Glucose↗
PubMed1979

Chronic diphenylhydantoin therapy does not reduce plasma 25-hydroxy-vitamin D.

A randomized controlled study was performed to investigate the effect of 2 years' monitored diphenylhydantoin (DPH) therapy on plasma 25-hydroxyvitamin D (25-OHD) in non-epileptic, non-institutionalized subjects. Mean +/- SEM plasma 25-OHD of 18 DPH-treated subjects at the end of 2 years' drug treatment was 59 +/- 8 nmol/l (23.6 +/- 3.2 ng/ml), which was not decreased compared to that of eighteen control subjects (54 +/- 8 nmol/l, 21.6 +/- 3.2 ng/ml). In addition, mean plasma 25-OHD had not changed 1 month after ceasing DPH. The treated group had a higher mean serum alkaline phosphatase (SAP) during DPH treatment, attributable to hepatic enzyme induction. It is concluded that therapeutic doses of DPH without other anticonvulsants do not have a clinically significant effect on plasma 25-OHD.

Adult↗
PubMed1978

Verapamil: a review of its pharmacological properties and therapeutic use.

Verapamil is a novel antiarrhythmic and antianginal agent which, although introduced in 1962, has only recently gained prominence not only as a significant agent in cardiovascular therapeutics but also as a powerful tool to examine the nature of some of the biophysical phenomena at the membrane of cardiac and other excitable tissues. Verapamil is the prototype of those agents which selectively inhibit membrane transport of calcium, an action which accounts for the drug's peripheral and coronary vasodilator properties, its effect on excitation-contraction coupling and hence its negative inotropic propensity, as well as its depressant effects on the sinus node and atrioventricular conduction. Its pharmacological effects are largely independent of the autonomic nervous system. The main therapeutic uses of the drug are in the management of atrial tachyarrhythmias, angina, and possibly hypertension. The overall exp:rimental and clinical data suggest that verapamil will become an important and safe addition to existing drug regimens, especially as an agent of choice for the short-term treatment of most cases of paroxysmal supraventricular tachycardias. The initial experience in other arrhythmias, angina and hypertension, is also sufficiently encouraging to justify further detailed clinical trials to define its potential role in cardiovascular therapeutics.

Angina Pectoris↗
PubMed1977

Thyroid hormone levels and protein binding in patients on long-term diphenylhydantoin treatment.

The effect of long-term diphenylhydantoin (DPH) treatment on thyroid hormone concentrations and protein binding was determined in a randomized controlled trial. As has been demonstrated previously, total thyroxine (T4) concentrations were significantly depressed in patients on DPH. There was no significant effect on indirect indices of protein binding of thyroid hormones, and the free thyroxine index (FTI) was also significantly depressed. Triiodothyronine (T3) and thyrotrophin (TSH) concentrations were either unaffected, or only very slightly affected by DPH. Significant effects on the FTI were still apparent 4 weeks after discontinuing treatment. It is concluded that the depression of total T4 levels observed in vivo is not due solely to diminished protein binding, but may instead be largely explained by reports suggesting enhanced degradation of T4 following DPH therapy.

Adult↗
PubMedDate not supplied

Hemodynamic adaptation to orthostatic stress after orthotopic heart transplantation.

OBJECTIVES: The purpose of this study was to compare the effects of orthostatic stress on cardiovascular stability in heart transplant recipients early and late after transplantation and in healthy controls. BACKGROUND: After transplantation, cardiac reinnervation is heterogeneous, with reports of sympathetic reinnervation after 5 months and parasympathetic reinnervation after 2 to 3 years. METHODS: Sixteen heart transplant recipients early (less than 5 months) after transplantation, 17 recipients late (1 year or more) after transplantation, and 16 matched healthy controls were subjected to 45 minutes of passive upright tilt, with the following variables measured before, during, and after the procedure: cardiac output, heart rate, stroke volume, mean arterial pressure, systemic vascular resistance, and plasma norepinephrine. RESULTS: At rest, heart rate (p < 0.0005) and mean arterial pressure (p = 0.003) were higher, and stroke volume was lower (p < 0.0005), in transplant recipients than they were in controls. With orthostasis, heart rate increased by 30% in controls and by 23% in the late posttransplantation group compared with 13% in the early posttransplantation group (p = 0.028); drop in stroke volume was three times more among controls than among those in either transplantation group (p < 0.001); late transplant recipients had higher norepinephrine increases than did the other two groups (p = 0.012). CONCLUSION: With the exception of heart rate, patterns of hemodynamic response to orthostatic stress after transplantation remain consistent over time and differ from controls. Among transplant recipients, higher mean arterial pressure mitigates the force of gravity and prevents drops in stroke volume. Clinicians may anticipate that transplant recipients will tolerate postural maneuvers well. Later after transplantation, however, orthostatic tolerance is associated with increased norepinephrine release, consistent with enhanced sympathoactivation.

Adaptation, Physiological↗
PubMedDate not supplied

Evidence of time-dependent autonomic reinnervation after heart transplantation.

BACKGROUND: Confirming the clinical significance of reinnervation is important in understanding and anticipating how heart rate (HR) responses of transplant recipients to physiologic stress differs early and late after transplant from that of normal individuals. OBJECTIVES: To evaluate the functional significance of cardiac reinnervation early and late after heart transplantation. METHODS: Handgrip and deep breathing tests, passive 80 degrees head-up tilt, and heart rate (HR) responsiveness of 33 transplant recipients (n = 16 at < 5 months and n = 17 at > 1 year after transplant) were compared with those of 16 age- and sex-matched control participants. RESULTS: HR responses to handgrip and passive tilt were absent early after transplant. HR acceleration normalized but was blunted late after transplant. These findings are consistent with late (>1 year) sympathetic reinnervation in transplant recipients. CONCLUSIONS: When caring for transplant recipients, nurses should consider the time elapsed since transplant in evaluating HR responsiveness to common procedures and interventions.

Analysis of Variance↗
PubMedDate not supplied

Role of electrophysiologic evaluation in patients with ventricular arrhythmias.

The decision to perform electrophysiologic testing in patients with ventricular arrhythmia should be based on the presence, if any, of underlying heart disease and the clinical type of ventricular arrhythmia. Clinical presentations range from asymptomatic premature ventricular complexes identified on routine surface ECG to out-of-hospital cardiac arrest. Ventricular arrhythmias range from benign monomorphic ventricular ectopy to polymorphic VT and ventricular fibrillation. The goal in evaluating patients with ventricular arrhythmia is to identify those at high risk of suffering a life-terminating arrhythmic event. Risk stratification should be based on history, physical examination, clinical data and the likelihood that anti-arrhythmic therapy will prevent symptoms and more importantly, prolong life. Noninvasive evaluation with routine surface ECG, Holter monitoring, signal-averaged ECG and echocardiography are valuable tools in the risk stratification process. However, electrophysiologic testing in most forms of ventricular tachyarrhythmia is the optimal means of diagnosing, risk stratifying and managing potentially life-threatening ventricular arrhythmias.

Electrocardiography↗