Yonsei Med J.  2006 Oct;47(5):672-679. 10.3349/ymj.2006.47.5.672.

The Effect of Cryoinjury on Ventricular Tachycardia in the Swine Right Ventricle

• Joung B
• Xu Z
• Kim I
• Lee MH
• Kim S

• KMID: 1381248
• DOI: http://doi.org/10.3349/ymj.2006.47.5.672

Abstract

This study was performed to assess the influence of the cryoinjury on the dynamics of wavefronts and to determine whether they can convert ventricular fibrillation (VF) to ventricular tachycardia (VT) in fibrillating right ventricular (RV) of swines using an optical mapping system. A cryoinjury with a diameter of 12 mm was created on the epicardium of perfused RV of swines (n = 6) and optical mapping were taken from baseline until 10 minutes after the cryoinjury. Out of 35 cryoinjuries, the images were possible to be interpreted in 32. The optical action potential could not be observed in either the cryoinjury or peri-injury sites at 1 and 3 minutes, was observed in only the cryoinjury site at 5 minutes, and recovered in both sites at 10 minutes. The cycle length of the tachycardia was 135.9 +/- 23.6 msec at baseline, 176.2 +/- 79.3 msec at 1 minute, 187.6 +/- 97.9 msec at 3 minutes, 185.5 19.2 msec at 5 minutes, and 152.1 +/- 64.1 msec at 10 minutes. The cycle lengths at 1, 3, and 5 minutes after the cryoinjury were significantly more prolonged than that at baseline (p = 0.001, p = 0.006, p = 0.016). After the cryoinjury, the VF changed to VT in 9 (28.0%), and terminated in 2 (6.3%). These changes were observed mainly within 5 minutes after cryoinjury. The cryoinjury had anti-fibrillatory effects on the tissue with VF. This phenomenon was related to a decreasing mass and stabilizing wavefronts.

Keyword

Activation mapping of arrhythmias; ventricular tachycardia/fibrillation

MeSH Terms

Ventricular Fibrillation/*physiopathology
Tachycardia, Ventricular/*physiopathology
Swine
Heart Ventricles/*physiopathology/surgery
Female
Disease Models, Animal
*Cryosurgery
Animals

Figure

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  Fig. 1 Optical fluorescent signal arranged by time sequences after the cryoinjury in pig No.5. (A. Raw image) The previous ventricular fibrillation (B. Baseline) was terminated and changed to ventricular tachycardia (C, D, E, F). The cycle length of tachycardia was increased after the cryoinjury and gradually reduced as time went on. The fluorescence signals of the periinjury zone (③) and cryoinjury site (④) were recovered after 5minutes (D) and 10 minutes (E) of the cryoinjury, respectively.

• 

  Fig. 2 Intermittent conduction block and attachment of wavefronts. (A) Consecutive optical map snapshots from Pig No. 2 after 3 minutes of the cryoinjury (circle). Wavefronts were initiated from the right upper region (①) and then propagated to the left lower region (④). Some waves were blocked (*) and attached at the cyoinjury site(†). (B) The local voltage signals (in fluorescence) at selected locations (circled numbers). Some signals were blocked. The signals that conducted were delayed at the peri- injury (②) or injury sites (③).

• 

  Fig. 3 A clockwise rotation of a wavefront after cryoinjury. (A) Consecutive optical map snapshots from pig No. 5 after 5 minutes of the cryoinjury (circle). A wavefront initated from the left upper region, then rotated clockwise for 10 beats. (B) The local voltage signals (in fluorescence) at selected locations (circled numbers). The signals were decreased at the cyoinjury site (②) as compared to the with reentry site (①). The shaded area represents the period during simultaneous optical mapping.

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  Fig. 4 Change in the cycle length according to the time after the cryoinjury (paired t-test with the Bonferroni correction). *p = 0.001 : change in the cycle length between that at baseline and 1 minute after cryoinjury. †p = 0.006. change in the cycle length between that at baseline and 3 minutes after cryoinjury. ‡p = 0.016 : change in the cycle length between that at baseline and 5 minutes after cryoinjury.

• 

  Fig. 5 Coexistance of idioventricular rhythm and ventricular fibrillation (A and B). Termination of ventricular fibrillation (C and D). A. C. Optical mapping of Pig No. 5 after 15 minutes of 4th cryoinjury (circle) showed wavefronts of idioventricular rhythm (white arrow) and ventricular fibrillation (yellow arrow). Optical fluorescent signal showed idioventricular rhythm (①) and ventricular fibrillation (②). Signal was not observed at the cryoinjury site (③). B. D. Optical mapping of pig No. 5 after 5 minutes of the 5th cryoinjury (circle). Idioventricular rhythm (white arrow) previously observed persisted. However, ventricular fibrillation was terminated. Optical florescent signal showed idioventricular rhythm (①). However, signal was not observed at previous ventricular fibrillation (②) and the cryoinjury site (③). Circular numbers represents sites where optical signals were taken in the raw image of upper panel. Shaded area represent the period of the simultaneous optical mapping.

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