Electrocardiographic and electrophysiologic characteristics of ventricular tachycardia originating within the pulmonary artery

ObjectivesWe investigated the electrocardiographic (ECG) and electrophysiologic characteristics of ventricular tachycardia (VT) originating within the pulmonary artery (PA).BackgroundRadiofrequency catheter ablation (RFCA) is routinely applied to the endocardial surface of the right ventricular outflow tract (RVOT) in patients with idiopathic VT of left bundle branch block morphology. It was recently reported that this arrhythmia may originate within the PA.MethodsActivation mapping and ECG analysis were performed in 24 patients whose VTs or ventricular premature contractions (VPCs) were successfully ablated within the PA (PA group) and in 48 patients whose VTs or VPCs were successfully ablated from the endocardial surface of the RVOT (RV-end-OT group).ResultsR-wave amplitudes on inferior ECG leads, aVL/aVR ratio of Q-wave amplitude, and R/S ratio on lead V2were significantly larger in the PA group than in the RV-end-OT group. On intracardiac electrograms, atrial potentials were more frequently recorded in the PA group than in the RV-end-OT group (58% vs. 12%; p < 0.01). The amplitude of local ventricular potentials recorded during sinus rhythm within the PA was significantly lower than that recorded from the RV-end-OT (0.62 ± 0.56 mV vs. 1.55 ± 0.88 mV; p < 0.01).ConclusionsVentricular tachycardia originating within the PA has different electrocardiographic and electrophysiologic characteristics from that originating from the RV-end-OT. When mapping the RVOT area, the catheter may be located within the PA if a low-voltage atrial or local ventricular potential of <1-mV amplitude is recorded. Heightened attention must be paid if RFCA is required within the PA

DEFINITION OF MIXING RATE OF INDICATOR BY INDICATOR DILUTION METHOD: EVALUATION OF RELATIONSHIP BETWEEN MIXING RATE OF INDICATOR AND CARDIAC OUTPUT DETERMINATION

It is generally agreed that complete mixing of the indicator is one of the most important factors of the indicator dilution method, however, no clear definition of the mixing state has been established. We established a formula for the mixing rate of the indicator by the indicator dilution method, using the concept of entropy in the information theory, and compared the mixing rate of indocyanine green in one mixing chamber (left ventricle) with that in the two mixing chamber system (including the aortic system). The mixing rate of the indicator (M) is shown as M(%)=100 H/Hcm -100 (lk Σn i=1 Ci log Ci +log k) (l & k: correction factors in each dye dilution curve, C: mean concentration of the indicator in the region).Left heart and aortic catheterizations by retrograde femoral and carotid artery approach were performed in five anesthetized dogs. Simultaneous dye dilution curves were recorded at the aortic root and at the bifurcation of the abdominal aorta, following the injection of indocyanine green (2.5 mg/lml of indocyamine green for each injection) by impulse into the left ventricle at the endsystole, triggered on the R wave of ECG, using the automatic injector devised by the authors. Twenty-five pairs of dye dilution curves were obtained by simultaneous recording in the aortic root and the abdominal aorta under several hemodynamic conditions, and the cardiac output, mean circulation time and the mixing rate of the indicator were determined.The mixing rate of the indicator obtained in the aortic root (mean±SE: M=78.7 ± 3.43%) was observed to be significantly greater (P<0.01) than in the abdominal aorta (mean ±SE: M=70.0±3.51%).Taking the mixing rate of the indicator into consideration, the cardiac output determination by the indicator dilution method is more sensitive to the changing hemodynamic conditions when determined in the aortic root than in the abdominal aorta