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Biomedical subjects

A D Sharma

Publications and source records attributed to A D Sharma.

At least 19 recordsLinked to original sources
PubMed2001

Dual AV nodal pathway physiology after injury with radiofrequency energy in a patient without a history of reentrant tachycardia.

Radiofrequency (RF) atrioventricular (AV) nodal modification has been reported to occasionally produce a proarrhythmic effect. Dual AV nodal pathway physiology in patients without reentrant tachychardia has also been reported. This case describes AV nodal modification with RF energy in an anatomically intermediate area resulting in the appearance of discontinuous antegrade conduction curves and reentry in a patient in which these were previously not present. This suggests that AV nodal injury may be a mechanism for acquired AV nodal reentry.

Atrial Fibrillation↗
PubMed2001

Reversible shear-mediated platelet dysfunction during cardiac surgery as assessed by the PFA-100 platelet function analyzer.

We undertook this investigation to assess alterations in shear-mediated platelet function during cardiac surgery and to determine the potential for the PFA-100 to predict post-operative bleeding. Platelet aggregation and PFA-100 closure times were determined in 18 adult patients at five intervals during cardiac surgery. Associations between post-operative bleeding and closure times were examined in an additional 58 patients. Statistical analysis consisted of Student's t, Wilcoxon signed rank, and Spearman correlation tests. All results are reported as mean +/- SEM. Collagen/epinephrine closure times were prolonged prior to and throughout surgery. Collagen/adenosine-5'-diphosphate (ADP) closure times were significantly prolonged by heparin administration, 141 +/- 15 s versus 115 +/- 10 s (P = 0.01), and subsequent initiation of cardiopulmonary bypass (CPB), 203 +/- 12 s (P= 0.0001); however, 15 min after protamine administration, closure times returned to near pre-operative values, 138 +/- 12 s (P = not significant). In contrast, platelet aggregation in response to ADP remained impaired in 17 of 19 patients after CPB. Neither ex vivo correction of sample hematocrits nor supplementation with Humate P affected closure times. Positive and negative predictive values for post-CPB collagen/ADP closure times to predict bleeding were 18 and 96%, respectively. These results suggest that factors both intrinsic and extrinsic to the platelet contribute to reversible shear-mediated platelet dysfunction during CPB, and that the PFA-100 may prove useful after CPB to identify patients unlikely to benefit from platelet transfusions.

Adenosine Diphosphate↗
PubMed2001

ANP, BNP, and CNP enhance bradycardic responses to cardiopulmonary chemoreceptor activation in conscious sheep.

We demonstrated previously that atrial natriuretic peptide (ANP) enhances reflex bradycardia to intravenous serotonin [5-hydroxytryptamine (5-HT)] (von Bezold-Jarisch reflex) in rats. To determine whether 1) ANP affects this cardiopulmonary vagal reflex in another species and 2) B-type (BNP) and C-type (CNP) natriuretic peptides share with ANP the ability to modulate this reflex, we used intravenous phenylbiguanide (PBG), a 5-HT(3) agonist, as the stimulus to evoke a von Bezold-Jarisch reflex (dose-related, reproducible bradycardia) in conscious adult sheep (n = 5). Three doses of PBG (13 +/- 3, 20 +/- 3, and 31 +/- 4 microg/kg) injected into the jugular vein caused reflex cardiac slowing of -7 +/- 1, -15 +/- 2, and -36 +/- 3 beats/min, respectively, under control conditions. These doses of PBG were repeated during infusions of ANP, BNP, or CNP (10 pmol. kg(-1). min(-1) iv), or vehicle (normal saline). Each of the natriuretic peptides significantly (P < 0.05) enhanced the sensitivity of bradycardic responses to PBG by 94 +/- 8% (ANP), 142 +/- 55% (BNP), and 61 +/- 16% (CNP). Thus not only did ANP sensitize cardiopulmonary chemoreceptor activation in a species with resting heart rate close to that in humans, but BNP and CNP also enhanced von Bezold-Jarisch reflex activity in conscious sheep.

Animals↗
PubMed2000

Surgical resection of an intracardiac rhabdomyoma.

There are only a few previous reports of intracardiac rhabdomyomas causing ventricular arrhythmias and near syncope. In this report we describe the successful surgical resection of an intracardiac rhabdomyoma using cardiopulmonary bypass, blood cardioplegia, and hypothermia. Preoperative evaluation consisting of echocardiography, computed tomography (CT), magnet resonance imaging (MRI), and positron emission tomography (PET) strongly suggested the presence of a symptomatic primary cardiac tumor projecting from the interventricular septum into the right ventricle.

Adult↗
PubMed1999

Anaesthetic pre-registration house officers: a survey of doctors and medical students opinions.

The GMC has accepted a proposal from the Royal College of Anaesthetists for a four-month module in anaesthesia, pain management and intensive care for pre-registration house officers. All 135 final year medical students at Aberdeen University and all GPs and hospital doctors (608 doctors) in the highland region of Scotland were sent a postal questionnaire asking their opinions on this module. Sixty-four per cent of medical students, 39% of hospital doctors and 22% of GPs replied. Eighty-three per cent of medical students would apply for the module if available. Eighty-eight per cent of doctors would have found the module useful in their careers. Sixty-seven per cent of doctors would recommend the module to trainees in their current speciality. This survey demonstrates a high level of support and interest in the module. This has considerable implications for the organisation of the pre-registration house officer year.

Anesthesiology↗
PubMed1996

Multicenter comparison of truncated biphasic shocks and standard damped sine wave monophasic shocks for transthoracic ventricular defibrillation. Transthoracic Investigators.

BACKGROUND: The most important factor for improving out-of-hospital ventricular fibrillation survival rates is early defibrillation. This can be achieved if small, lightweight, inexpensive automatic external defibrillators are widely disseminated. Because automatic external defibrillator size and cost are directly affected by defibrillation waveform shape and because of the favorable experience with truncated biphasic waveforms in implantable cardioverter-defibrillators, we compared the efficacy of a truncated biphasic waveform with that of a standard damped sine monophasic waveform for transthoracic defibrillation. METHODS AND RESULTS: The principal goal of this multicenter, prospective, randomized, blinded study was to compare the first-shock transthoracic defibrillation efficacy of a 130-J truncated biphasic waveform with that of a standard 200-J monophasic damped sine wave pulse using anterior thoracic pads in the course of implantable cardioverter-defibrillator testing. Pad-pad ECGs were also examined after transthoracic defibrillation. After the elimination of data for 24 patients who did not meet all protocol criteria, the results from 294 patients were analyzed. The 130-J truncated biphasic pulse and the 200-J damped sine wave monophasic pulse resulted in first-shock efficacy rates of 86% and 86%, respectively (P = .97). ST-segment levels measured 10 seconds after the shock in 151 patients in sinus rhythm were -0.26 +/- 1.58 and -1.86 +/- 1.93 mm for the 130- and 200-J shocks, respectively (P < .0001). CONCLUSIONS: We found that 130-J biphasic truncated transthoracic shocks defibrillate as well as the 200-J monophasic damped sine wave shocks that are traditionally used in standard transthoracic defibrillators and result in fewer ECG abnormalities after the shock.

Adolescent↗
PubMed1993

Creatinine elevation in patients receiving amiodarone correlates with serum amiodarone concentration.

Serum creatinine and drug concentrations were measured at 0, 1, 2, 3, 6, 9 and 12 months in 30 consecutive patients started on amiodarone. In 28 of these patients with no obvious cause for altered renal function, mean serum creatinine increased to 11% above baseline (P < 0.005). Rising creatinine concentrations correlated with amiodarone concentrations (y = 93.9 + 8.6x, r = 0.51, P < 0.0001). When assessing elevation of serum creatinine in a patient receiving amiodarone, physicians should be aware that it may be related to this drug.

Amiodarone↗
PubMed1992

The effects of sympathetic denervation on spontaneous ventricular defibrillation in the rat.

Ventricular tachycardia or ventricular fibrillation was electrically induced in 38 normal rats (group 1) and 24 sympathetically denervated rats (6-hydroxydopamine) (group 2). The time for spontaneous reversion to sinus rhythm was measured during (1) control, (2) isoproterenol, and (3) the combination of isoproterenol and phenylephrine. The time for spontaneous reversion was the same in both groups in the three states. The reversion time was prolonged threefold by isoproterenol, and restored to control values when phenylephrine was added to the infusion of isoproterenol. The tachycardia duration and the refractory period were inversely related: log10 (tachycardia duration) = 3.466-0.091 (refractory period). Ventricular tachycardia/fibrillation induction was examined as follows: (i) Ventricular tachycardia/fibrillation was induced in 100% of normal rats (group 1), but only 42% of the denervated rats (group 2, p less than 0.001); (ii) during isoproterenol, ventricular tachycardia/fibrillation was induced in 100% of rats of both groups; and (iii) when phenylephrine was added to isoproterenol, ventricular tachycardia/fibrillation was induced in 100% of group 1 rats versus 82% of group 2 rats, (p = NS). These observations suggest (1) the induction of ventricular tachycardia/fibrillation is highly dependent on intact sympathetic innervation, and (2) exogenous adrenergic agonists modulate the duration of ventricular fibrillation through their effects on ventricular refractory period, independent of sympathetic innervation.

Animals↗