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Biomedical subjects

A M Naik

Publications and source records attributed to A M Naik.

12 recordsLinked to original sources
PubMed2000

Are implantable cardioverter- defibrillators cost-effective?

Sudden cardiac deaths account for a large number of cardiovascular deaths, and ventricular tachyarrhythmias are implicated in many of these. In survivors of sudden cardiac deaths and other selected groups of patients, implantable cardioverter-defibrillators (ICDs) have been shown to have significant survival benefits in randomized controlled trials. The incremental costs for each extra year of survival conferred by ICDs were compared to the cost of antiarrhythmic drug therapy in some of these trials. In patients with nonsustained ventricular tachycardia with low ejection fraction (< 35%) and inducible sustained ventricular tachycardia on programmed electrical stimulation (nonsuppressible by procainamide), the incremental costs of ICD therapy amounted to $27,000 per life-year saved, compared with drug therapy. These costs may be acceptable increments for adaptation of the new technology in view of the definite survival advantage conferred by ICDs. Evolving technology may further reduce these costs by development of better devices with longer battery life.

Amiodarone↗
PubMed2000

Comparing cardiac action potentials recorded with metal and glass microelectrodes.

Machine-pulled high-impedance glass capillary microelectrode is standard for transmembrane potential (TMP) recordings. However, it is fragile and difficult to impale, especially in beating myocardial tissues. We hypothesize that a high-impedance pure iridium metal electrode can be used as an alternative to the glass microelectrode for TMP recording. The TMPs were simultaneously recorded from isolated perfused swine right ventricles with a metal microelectrode and a standard glass microelectrode during pacing and during ventricular fibrillation. The basic morphology of TMP recorded with these electrodes was comparable. The action potential duration (APD) at 90% repolarization was 241 +/- 29 ms for the metal microelectrode and 236 +/- 31 ms for the glass microelectrode with a good correlation (r = 0.99, P < 0.0001). The maximum slope value of the APD restitution curves during pacing was also significantly correlated. One metal microelectrode and >20 glass microelectrodes were needed per study. We conclude that, in isolated perfused swine right ventricles, the TMP recorded by the metal microelectrode is comparable with that recorded by the glass microelectrode. Because the metal microelectrode is more durable than the glass microelectrode, it can serve as an alternative for APD recording and for restitution analyses.

Action Potentials↗
PubMed1999

Dual morphology of idiopathic ventricular tachycardia.

INTRODUCTION: Idiopathic ventricular tachycardia (VT) typically has a single morphology originating either in the right ventricular outflow tract (RVOT) or near the posterior fascicle of the left ventricle (LV) in most instances. We present our observations in six patients with idiopathic VT in whom two morphologies were present. METHODS AND RESULTS: Of 55 patients with idiopathic VT who underwent radiofrequency (RF) ablation, 44 had LV "fascicular" tachycardia, whereas 11 had RVOT tachycardia. During RF energy delivery, there was a change in VT morphology in two patients with idiopathic LV tachycardia. This second morphology was not ablated initially, recurred at follow-up, and was reablated successfully. In two additional patients with idiopathic LV tachycardia, a second VT was inducible after ablation of the "clinical" VT. This second morphology recurred at follow-up and was ablated successfully in one patient. The site where the second VT was ablated in all the three patients was remote from that of the first VT. In two patients with RVOT tachycardia, a second VT, originating from a different area of the RVOT, was induced after RF ablation of the "clinical" VT. This second VT recurred at follow-up and was reablated successfully in one patient. CONCLUSION: Idiopathic VT is a more heterogenous entity than hitherto believed. A second VT was seen in 11% of patients during or after RF ablation of the "clinical" VT. The appearance of a second VT suggests either a different exit site of the same circuit or another site of origin.

Adolescent↗
PubMed1999

Age at onset, gender distribution and intraarterial blood pressure changes in atrioventricular node-dependant tachycardias.

OBJECTIVE: Atrioventricular nodal reentrant tachycardia (AVNRT) and atrioventricular reentrant tachycardia (AVRT) utilising accessory pathways constitute the vast majority of paroxysmal supraventricular tachycardia (SVT). We studied the age at onset, the gender distribution and the intraarterial hemodynamics of these tachycardias. METHODS: The data of 224 patients who underwent electrophysiology study (EPS) and radiofrequency ablation was analysed. The age at onset of tachycardia was assessed by a careful history. The intraarterial BP was noted during sinus rhythm (SR), immediately after tachycardia onset (T0) and 15 seconds after the onset of tachycardia (T15). RESULTS: The age at onset of tachycardia was a decade later for AVNRT (48 +/- 10 years) than for AVRT (37 +/- 11 years). There was no gender preponderance in the AVNRT group (60 males, 56 females) while a male preponderance was seen in the AVRT group (71 males, 37 females, p < 0.01). There was a marked fall in the intraarterial systolic BP in both groups at the onset of tachycardia, from 143 +/- 24 mm Hg to 108 +/- 16 mm Hg (p < 0.05) for AVNRT and from 139 +/- 25 mm Hg to 107 +/- 18 mm Hg (p < 0.05) for AVRT. There was no correlation between the rate of tachycardia and the extent of fall of BP. CONCLUSION: Hospital-based data in an Indian setting found a similar pattern of age of onset of AV node-dependant tachycardia as in Western literature. However, unlike in Western studies, no female preponderance was seen in the AVNRT group. The fall in systolic BP at the onset of tachycardia is significant, similar in the two groups and independent of the rate of tachycardia.

Adult↗
PubMedDate not supplied

Is haemorrhagic myocardial infarction more common with streptokinase?

Autopsy reports and clinical data of 226 consecutive myocardial infarction deaths in whom postmortem studies could be carried out during the period 1980 to 1996 were analyzed retrospectively for the presence of haemorrhagic myocardial infarction (HMI). Of 53 autopsies done from 1980 to 1986 [prior to use of streptokinase (SK) therapy in our institution] none of the specimens showed haemorrhagic infarction. Of 173 autopsies done from 1987 to 1996 (intravenous SK therapy was utilised in this period), 20 specimens showed haemorrhagic infarctions. Sixteen of these 20 patients had received SK, while 66 of the remaining 153 non-haemorrhagic myocardial infarction patients received SK (statistically significant association of SK with HMI, p < 0.005). Acute mechanical complications [ventricular septal rupture (n = 10), papillary muscle rupture (n = 2), cardiac free wall rupture (n = 7)] were seen in 19 cases. Of these, 16 were HMIs and 14 of these patients had received streptokinase. These observations suggest a strong association of HMI with SK therapy and with acute mechanical complications.

Adult↗
PubMedDate not supplied

Scope and efficacy of complex radiofrequency ablation.

Radiofrequency ablation is an effective treatment for various tachycardias. In some patients undergoing radiofrequency ablation, there are additional complexities. Of 254 consecutive patients (161 males, 93 females, aged 38 +/- 15 years) who underwent radiofrequency ablation, two groups were identified. Patients with structural heart disease, multiple accessory pathways, multifocal idiopathic ventricular tachycardia, parahisian accessory pathways, and multiple mechanisms of tachycardia were considered as complex radiofrequency ablation (Group I) and the remaining as non-complex radiofrequency ablation (Group II). There were 23 patients in Group I. The overall success rate was not different in the two groups: 20/23 (87%) vs 208/231 (90%) in groups I and II, respectively. The procedure and fluoroscopy time (212 +/- 91 min vs 136 +/- 45 min; p = 0.0001; and 55 +/- 31 min vs 31 +/- 21 min; p = 0.001, respectively) were significantly longer in Group I. There was a higher recurrence rate in Group I (6/20, 30% vs 20/208, 9.6%; p = 0.02); repeat radiofrequency ablation was successfully performed in four patients with recurrence in Group I. Complications were rare in both the groups. There was no mortality. Thus radiofrequency ablation in complex situations was effective, though more demanding than non-complex radiofrequency ablation and associated with higher recurrence.

Adolescent↗
PubMedDate not supplied

Arrhythmogenic right ventricular dysplasia: electrophysiologic and morphologic features in nine patients.

Arrhythmogenic right ventricular dysplasia is a potentially life-threatening disorder, not previously well described in India. We analysed the electrocardiographic, electrophysiologic, angiographic, signal-averaged electrocardiogram and magnetic resonance imaging features of nine patients having arrhythmogenic right ventricular dysplasia at our centre. There were seven males and two females, aged 25 to 55 years. Eight patients presented with sustained monomorphic ventricular tachycardia. The electrocardiogram showed prolonged QRS duration in four, T inversion in leads V2-V3 in four, and epsilon wave in two patients. Abnormal late potentials were present in eight patients. During electrophysiologic study in seven patients, 13 different VTs were induced. Seven patients had right ventricular dilatation and dysfunction and left ventricular involvement was seen in three patients. Eight patients were treated with amiodarone, including one who received an implantable cardioverter-defibrillator. At a follow-up of 8.6 +/- 5.3 months, there was no death, while one patient had recurrence of ventricular tachycardia. Arrhythmogenic right ventricular dysplasia seems to predominantly affect middle-aged men, the presentation most often being sustained monomorphic ventricular tachycardia. Depolarisation and/or repolarisation abnormalities in the electrocardiogram are commonly present. Multiple ventricular tachycardia morphologies during electrophysiologic study and abnormal right ventricular angiograms are usually observed.

Adult↗