Biomedical subjects

B Boveja

Publications and source records attributed to B Boveja.

6 recordsLinked to original sources

PubMed2000

Electroanatomic mapping to identify breakthrough sites in recurrent typical human flutter.

The accuracy of conventional techniques in localizing previous radiofrequency (RF) ablation sites and thus breakthrough sites of recurrent atrial flutter is somewhat limited. We investigated the role of electroanatomic mapping for identifying breakthrough sites or "gaps" at the tricuspid annulus and inferior vena cava (IVC)/eustachian ridge isthmus to help RF ablation in patients with recurrent typical flutter. Twelve patients (8 men, 4 women, age 63 +/- 10 years) with recurrent typical atrial flutter were included in the study. An electroanatomic mapping system (CARTO) was used to create a voltage map and activation and propagation patterns in the right atrium. Detailed voltage, activation, and propagation mapping of the tricuspid annulus and IVC/eustachian ridge isthmus allowed precise identification of gaps in all 12 patients at the tricuspid annulus (eight sites), IVC ridges (two sites), mid-isthmus region (one site), and tricuspid annulus and IVC ridges (one site). Radiofrequency energy directed at these sites eliminated atrial flutter in all 12 patients, confirmed by noninducibility of atrial flutter and demonstration of conduction block during atrial pacing on either side of the lesion lines. During a mean follow-up of 14.8 +/- 3.5 months (range 8-19 months), paroxysmal atrial flutter recurred in only one patient and was subsequently treated with amiodarone, although this had been ineffective prior to ablation. Electroanatomic mapping can precisely identify gaps in the lesion line responsible for breakthrough of recurrent typical atrial flutter at the tricuspid annulus and at the IVC/eustachian ridge isthmus. These sites can be targeted with RF ablation with a high degree of success.

Atrial Flutter↗

PubMed1991

Ventricular and atrial defibrillation using new transvenous tripolar and bipolar leads with 5 French electrodes and 8 French subcutaneous catheters.

This study evaluated the use of new small transvenous atrial and ventricular leads for converting atrial fibrillation (AF) and ventricular fibrillation (VF) in 10 adult male mongrel dogs. Five dogs (group A) received a right atrial "J" (AJ) and right ventricular (RV) active fixation tripolar lead, each consisting of a platinized platinum pacing tip, anode band, and braided defibrillation electrode. The remaining five dogs (group B) received one bipolar RV lead and one tripolar AJ lead. The RV leads were implanted in the right ventricular apex (RVA) and the AJ leads were placed in the atrial appendage. Additionally all dogs received two 8 French subcutaneous defibrillation catheters in the fifth and seventh intercostal spaces. Twenty asymmetric biphasic shocks consisting of five randomized voltage levels were used to convert VF in groups A and B. The bipolar RV lead (group B) had a significantly higher probability of success in converting VF than the tripolar RV lead (group A). In group A defibrillation thresholds for converting AF were obtained using two electrode configurations. No significant difference was observed between the two electrode configurations used to convert AF. Pacing and sensing thresholds were satisfactory for bipolar and tripolar lead configuration.

Animals↗

PubMed1989

The ventricular depolarization gradient: effects of exercise, pacing rate, epinephrine, and intrinsic heart rate control on the right ventricular evoked response.

A new pacing technique is described that permits high fidelity recording of the paced ventricular evoked response, including cardiac depolarization. Integration of the paced R wave yields the ventricular depolarization gradient (GD), which is dependent on activation sequence and the spatial dispersion of activation times. GD was studied in 27 dogs to determine the effects of treadmill exercise at fixed rate pacing (n = 10), elevation of heart rate in the absence of stress (n = 20), epinephrine at fixed rate (n = 6), and exercise in the presence of normal chronotrophic response (n = 7). Low level exercise (1 mph, 2 min, 15 degrees) at a fixed heart rate produced significant (P less than 0.0005) decreases in GD that averaged -10.8 +/- 4.0% (mean +/- SD). The rate of change in GD was faster at the onset of exercise than at its cessation (P less than 0.0005). Artificial elevation of heart rate at rest produced significant (P less than 0.0005) increases in GD; mean sensitivity of GD to rate was 0.27 +/- 0.12%/beats/min. Intravenous injection of epinephrine produced significant (P less than 0.001) decreases in GD at two dosage levels (2.5 and 5.0 micrograms/kg) when evaluated at two baseline pacing rates (150 and 190 beats/min); mean changes in GD were -20.64 +/- 0.53% (2.5 micrograms/kg at 150 beats/min), -25.19 +/- 4.20% (5.0 micrograms/kg at 150 beats/min), -14.18 +/- 5.19% (2.5 micrograms/kg at 190 beats/min), and -24.22 +/- 4.94% (5.0 micrograms/kg at 190 beats/min). Sensitivity of GD to epinephrine was dose-dependent (P less than 0.01) at each baseline rate, but was independent (P greater than 0.05) of the rate itself. In the presence of a normal chronotropic response, GD remained unchanged (P greater than 0.5) during exercise in spite of significant elevation in heart rate (105.0 to 167.1 beats/min, P less than 0.001). These data suggest the presence of an intrinsic negative-feedback control mechanism that maintains GD constant in the healthy heart during homeostatic disturbance. Applications in closed-loop rate adaptive pacing are described.

Animals↗

PubMed1987

Low-energy transvenous ablation of the canine atrioventricular conduction system with a suction electrode catheter.

A single suction electrode catheter was used for His bundle electrogram recording. His bundle pacing, and low-energy (20 or 30 J) His bundle ablation in seven dogs. The suction electrode catheter was actively fixed to the atrial endocardium at the His bundle level. Electrophysiologic studies were performed in the control state, immediately after, and late (greater than 40 days) after His bundle ablation and results were correlated with histologic findings in the conduction system. Unipolar His bundle recording and pacing were successfully performed in all dogs with the suction electrode catheter before and after ablation. Complete heart block developed after a single 20 J shock delivered via the suction electrode catheter in all dogs immediately, but reverted to 1:1 atrioventricular conduction with first-degree atrioventricular block in two dogs in which one or two additional shocks (20 or 30 J) produced complete heart block. Mean ablation energy per shock was 22 +/- 4 J. The mean total delivered energy per dog was 31 +/- 20 J. Late electrophysiologic study in all dogs showed persistent complete heart block in five dogs and paroxysmal second-degree or third-degree atrioventricular block in two dogs. Gross examination of the ablation site showed a white plaque above the medial tricuspid leaflet (1.4 to 2.0 cm long and 0.4 to 0.6 cm wide). Microscopically, fibrosis of the penetrating and branching His bundle was seen in all dogs, with minimal atrioventricular node and atrial involvement. Significant proximal right bundle branch fibrosis was observed in the two dogs receiving one or two additional shocks. We conclude that the suction electrode catheter permits repeated His bundle recording, pacing, and ablation with a single catheter. Permanent and safe low-energy ablation of the canine His bundle is feasible. Focal injury localized to the target area in the conduction system can be obtained.

Animals↗

PubMed1986

An experimental device for low-energy, precise ablation of AV conduction.

A combination suction catheter-bipolar lead system permits precise ablation of AV conduction with low energy. The electrode is positioned to maximize the bipolar His potential, then to maximize the HP between the tip and a surface electrode. With the tip held in place by 100-200 mmHg of suction, this site is paced. If the St-V interval is short and the ventricular morphology is similar to a sinus beat, a shock of 10 or 20 J is delivered. If complete heart block does not result, additional shocks are delivered. The device was used in eight dogs. When the St-V was close to the unpaced H-V interval, a shock of 20 J always produced permanent CHB. In contrast, an initial shock of 10 J always failed, and more shocks of up to 30 J were required to produce CHB which, even then, did not always persist. At 60 days the hearts were healed with a round, white, dense scar of about 2 mm in diameter just above the leaflet of the tricuspid valve. This device can produce permanent dissociation of the atria and ventricles with a shock of 20 J. It also enables precise positioning of the electrode.

Animals↗

PubMed1979

Oxygen consumption in canine skeletal muscle following massive saline infusion.

To study the effect of interstitial edema on tissue oxygen transport, we infused buffered isotonic saline solution at a rate of 200 ml/kg/hr into mongrel dogs for two hours, measuring oxygen delivery and consumption in a skinned, innervated hindlimb. Hematocrit dropped gradually to 10.8 +/- 3.9%. Muscle water content increased 13% (P less than 0.05). However, oxygen consumption did not change significantly from control of 0.228 +/- 0.029 ml/min/100 gm. Femoral venous oxygen tension fell from control of 62.6 +/- 2.6 mm Hg to 31.4 +/- 2.3 mm Hg. Mean arterial flow increased to nearly twice the control level of 12.5 +/- 1.1 ml/min/100 gm and fell gradually, with the sustained 50% drop in vascular resistance largely explained by expected decreases in blood viscosity. We conclude that interstitial edema did not cause a significant defect in canine skeletal muscle oxygen utilization.

Animals↗