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Articles by K. Nanthakumar
Total Records ( 2 ) for K. Nanthakumar
  S. C Toal , T. A Farid , R Selvaraj , V. S Chauhan , S Masse , J Ivanov , L Harris , E Downar , M. R Franz and K. Nanthakumar

Background— Action potential duration (APD) variation is an important determinant of wave break and reentry. The determinants of APD variability during early ventricular fibrillation (VF) in myopathic human hearts have not been studied. The objective of this study was to study the role of APD restitution and short-term cardiac memory on variation in human VF.

Methods and Results— The study consisted of 7 patients (67±9 years old) with ejection fraction <35%. Monophasic action potentials were recorded from the right and/or left ventricular septum during VF. APD60/90 was measured in sinus beat preceding induction of VF, and its amplitude was used to define 60%/90% repolarization in VF. The monophasic action potential upstroke (dV/dtmax) was used to characterize local excitability. Simple linear regression showed that variability in APDn60 was determined by APD/diastolic interval restitution (R2=0.48, P<0.0001) and short-term memory (APD60 n–1, n–2, n–3, n–4; R2=0.55, 0.40, 0.33, and 0.27 respectively; P<0.001). Using multiple stepwise regression, short-term memory and restitution accounted for 62% of variance in APD60 (P<0.001). Individually, memory effect had the greatest contribution to APD variability (R2=0.55, P<0.0001).

Conclusions— In early human VF, short-term memory and APD/diastolic interval restitution explain most of the APD variability, with memory effects predominating. This suggests that in early human VF, short-term cardiac memory may provide a novel therapeutic target to modulate progression of VF in myopathic patients.

  N. Ramesh , V. Rajesh Kannan , K. Karthikeyan , K. Nanthakumar and R. Karthik Raja
  Isolation of Bluetongue virus from blood samples of sheep and goat was carried out in the present study. Out of one fifty blood samples screened for seroprevalance of BTV antibodies by Agarose Gel Precipitation Test (AGPT) 42 gave positive results. The overall percentage of virus isolation was 28% from Embryonated Chicken Eggs (ECE). The identities of the isolates were confirmed by cytopathogenicity. All the isolates were passaged twenty one times in embryonated chicken eggs and further passaged in BHK-21 cell lines. The viral isolates adapted well to the cell culture system and produced cytopathic change like grouping of cells, polycaryon, syncytica formation, acidophilic and intracytoplasmic inclusion bodies in BHK-21 cells. This study confirms the BTV incidence in the tested blood sample with a possible means showing that the virus can easily adapt to ECE and BHK-21 cell line.
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