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CLINICAL STUDY

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

Manuscript received February 2, 2000; revised manuscript received November 17, 2000, accepted December 20, 2000.

Reprint requests and correspondence: Dr. Takeshi Tsuchiya, Cardiovascular Center Saiseikai Kumamoto Hospital, Chikami 5-3-1, Kumamoto City, 861-4193 Japan
tsuchit{at}mvc.biglobe.ne.jp

OBJECTIVES

We characterized pharmacologically the slow conduction zone of verapamil-sensitive idiopathic left ventricular tachycardia (ILVT) with regard to the late diastolic potential (LDP).

BACKGROUND

We showed that the slow conduction zone of ILVT could be divided into two components by LDP; that is, the distal component with a tachycardia-dependent conduction delay property and the proximal one without it.

METHODS

Electrophysiologic studies were performed in eight consecutive patients. The LDP was recorded during left ventricular (LV) mapping during ILVT. Entrainment was performed from the right ventricular outflow tract while recording LDP. The effects of lidocaine (1 mg/kg body weight) and verapamil (0.5 or 1.0 mg) were examined during entrainment.

RESULTS

The LDPs preceding the Purkinje potential (PP) were serially recorded from the upper third to the middle of the LV septum along the narrow longitudinal line. The ventricular tachycardia (VT) cycle length increased after lidocaine (p < 0.05), and further after verapamil (p < 0.05). The increments in the VT cycle length after administration of the drugs strongly correlated with those in LDP-PP (r > 0.9 for both drugs). The interval from the ventricular potential to LDP was unchanged after administration of the drugs. In one patient, verapamil terminated VT by local conduction block between LDP and PP. The LDP-PP measured during entrainment increased after lidocaine, and further after verapamil, whereas the interval from the stimulus to LDP remained unchanged.

CONCLUSIONS

The component distal to LDP is mainly calcium channel-dependent and partly depressed sodium channel-dependent. The proximal component is considered to be sodium channel-dependent (normal).

Abbreviations and Acronyms   ILVT = idiopathic left ventricular tachycardia   LDP = late diastolic potential   LV = left ventricular   PP = Purkinje potential   RV = right ventricular   RVA = right ventricular apex   RVOT = right ventricular outflow tract   st = stimulus   VP = ventricular potential   VT = ventricular tachycardia

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