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Effects of verapamil and lidocaine on two components of the re-entry circuit of verapamil-sensitive idiopathic left ventricular tachycardia

Takeshi Tsuchiya, MD^*, Ken Okumura, MD, Toshihiro Honda, MD^*, Atsushi Iwasa, MD and Keiichi Ashikaga, MD^*

^* Cardiovascular Center, Saiseikai Kumamoto Hospital, Kumamoto, Japan
Second Department of Internal Medicine, Hirosaki University School of Medicine, Hirosaki, Japan

View larger version (36K): [in a new window]   Figure 1 Examples of late diastolic potentials (LDPs) (arrows) preceding Purkinje potential (PP) in four patients (cases 1, 4, 5 and 6), recorded serially from the middle to upper third of the left ventricular (LV) septum along the narrow longitudinal line during ventricular tachycardia (VT). Tracings are electrocardiographic leads I, II and V1, and intracardiac electrograms are recorded from the His bundle region (His), right ventricular apex (RVA), right ventricular outflow tract (RVOT) and eight-electrode catheter located in the LV septum (LV1 to LV8). All numbers are in ms. A = atrial potential; H = His bundle potential.

View larger version (18K): [in a new window]   Figure 2 Correlations of the increases in VT cycle length (CL) with those of the intervals from LDP to PP (LDP-PP) after lidocaine (1 mg/kg) and verapamil (0.5 or 1.0 mg). There were significant correlations between the increases in VT cycle length and those in LDP-PP after lidocaine and verapamil (r = 0.98, p = 0.0006 for control study vs. post-lidocaine; r = 0.93, p = 0.0009 for pre-verapamil vs. post-verapamil). Abbreviations as in Figure 1.

View larger version (69K): [in a new window]   Figure 3 A beat-to-beat variation in the VT cycle length occurred after intravenous administration of verapamil (1 mg). Tracings are ECG leads I, II, III, aVF and V1, and intracardiac electrograms are recorded at the RVOT and RVA, with the distal and proximal pairs of the mapping catheter where LDP was recorded (proximal and distal LDP sites), as well as ECG lead V5. Note that the VT cycle length and the interval from LDP to PP were variable, whereas the intervals from PP to the local ventricular potential (VP) and from VP to LDP were almost constant. It is also noted that VT was finally terminated due to local conduction block between the LDP and PP recording sites. All numbers are in ms. Abbreviations as in Figure 1.

View larger version (33K): [in a new window]   Figure 4 Examples of entrainment by pacing from the RVOT at a rate of 145 beats/min while recording LDP during the control study (upper panel), after lidocaine administration (middle panel) and after verapamil administration (lower panel). Tracings are ECG leads I, II and V1, and intracardiac electrograms are recorded at the His bundle region (His), RVOT, RVA and LDP site (arrows). All numbers are in ms. The numbers in circles indicate conduction intervals from the LDP stimulus artifact (st) to the electrogram at the RVA and from LDP to PP. See text for discussion. Abbreviations as in Figure 1.