Publications (2)7.16 Total impact
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Article: Effect of right bundle branch block on electrocardiographic amplitudes, including combined voltage criteria used for the detection of left ventricular hypertrophy.
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ABSTRACT: Although right bundle branch block (RBBB) delays right ventricular depolarization, its effect on cancellation of right and left ventricular forces within the QRS complex has not been quantified during stable temporal and physiological conditions. Systematic changes in QRS amplitude during transient RBBB bear directly on performance of standard ECG criteria for left ventricular hypertrophy (LVH), and these changes require quantification. We examined the instantaneous effect of RBBB on QRS amplitudes and LVH voltages in 40 patients who had intermittent complete RBBB during a single 10 sec standard 12-lead ECG recording, comprising 0.1% of approximately 400,000 consecutive ECGs in a university teaching hospital setting. Amplitudes were measured by magnifying graticule to the nearest 25 microvolts, averaged for up to 3 normal and 3 RBBB complexes, and compared by paired t test. RBBB was associated with an increase in initial QRS forces (RV1, RV2, and QV6) but significant decreases in mean mid-QRS amplitudes that reflect left ventricular depolarization (RaVL [-75 microvolts], SV1 [-389 microvolts], SV3 [-617 microvolts], RV5 [-100 microvolts], and RV6 [-123 microvolts]). All late QRS forces were increased with RBBB (R'V1, SV5, SI). As a result, combined voltages used for LVH criteria were significantly reduced by RBBB: Sokolow-Lyon voltage decreased from 1520 +/- 739 to 1014 +/- 512 microvolts (p < 0.001), and Cornell voltage decreased from 1438 +/- 683 to 746 +/- 399 microvolts (p < 0.001). RBBB is associated with significant reduction in "left ventricular" QRS amplitudes of the standard ECG, consistent with cancellation, rather than unmasking, of left ventricular mid-QRS forces by altered septal and delayed right ventricular depolarization. Because QRS voltages that are routinely combined for the detection of LVH are reduced in RBBB, standard LVH criteria will perform with lower sensitivity in patients with RBBB.Annals of Noninvasive Electrocardiology 07/2006; 11(3):230-6. · 1.10 Impact Factor -
Article: Coronary patency and its relation to contractile reserve in hibernating myocardium.
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ABSTRACT: Recent clinical studies suggest that contractile reserve may occur in a minority of viable, chronically dysfunctional segments with reduced resting flow (hibernating myocardium). We hypothesized that epicardial artery patency might predict which segments have critically reduced subendocardial flow reserve and limited contractile reserve. Pigs were chronically instrumented with a fixed stenosis on the left anterior descending coronary artery (LAD) to produce hibernating myocardium. At least 3 months later, flow at rest and during adenosine vasodilation (microspheres), ventricular function and contractile reserve (contrast ventriculography), and (18)F-2-deoxyglucose (FDG) deposition (ex vivo tissue counting) were quantified. Hibernating myocardium (regional dysfunction with reduced resting perfusion) was present in animals with an occluded (n=40) or patent (n=19) LAD. Viability was confirmed by histology and FDG deposition. In collateral-dependent hibernating myocardium, subendocardial flow did not increase above baseline levels during epinephrine or adenosine stimulation, consistent with exhausted subendocardial flow reserve at rest. This was associated with limited contractile reserve and regionally increased FDG deposition. In contrast, subendocardial flow reserve was present in hibernating myocardium distal to a patent artery. Contractile reserve during epinephrine infusion in this group was significantly greater than in animals with an occluded artery. The physiology and metabolism of hibernating myocardium was dependent upon stenosis severity and its effects on subendocardial flow reserve. In collateral-dependent hibernating myocardium, contractile reserve was limited in the setting of exhausted subendocardial flow reserve, thus supporting the hypothesis that metabolic imaging may be preferable for determining viability distal to a complete occlusion.Cardiovascular Research 08/2002; 55(1):131-40. · 6.06 Impact Factor
