Histopathological changes post cryoablation in canine myocardium / 中华心血管病杂志

<p><b>OBJECTIVE</b>The purpose of this study was to observe histopathological changes post cryoablation in canine myocardium, to characterize the specific ablation lesion post cryoablation.</p><p><b>METHODS</b>Cryothermal ablation was applied on myocardium (both epicardium and endocardium) of 14 mongrel dogs with different ablation parameters (-25 degrees C x 4 min, -50 degrees C x 4 min, -75 degrees C x 4 min, -75 degrees C x 2 min, -75 degrees C x 6 min, -75 degrees C x 8 min). Lesion dimensions and histopathologic changes were observed.</p><p><b>RESULTS</b>The discrete, sharply delimited lesions were detected in cryoablated myocardium. Histologically, cryoablation in all temperatures studied induced heterogeneous necrosis of the myocardium. Lesion dimensions are related to freezing time and temperature.</p><p><b>CONCLUSION</b>Cryoablation is a feasible and preferably choice for clinical application due to its controllable myocardium lesions.</p>

Comparison of different pacing sites of the right ventricle on left ventricular mechanical synchrony and systolic performance using tissue Doppler imaging / 中华心血管病杂志

<p><b>OBJECTIVE</b>Right ventricular apical pacing may induce cardiac desynchronize and deteriorate left ventricular systolic performance. We hypothesized that right ventricular outflow tract (RVOT) pacing could produce better mechanical synchrony and left ventricular contraction.</p><p><b>METHODS</b>We enrolled nine patients without structural heart disease who underwent electrophysiological studies. The pacing sites (right apex, low septum, free wall and septum of RVOT of the right ventricle) were defined with fluoroscopy and ECG. The atrioventricular sequential pacing was applied every 5 minutes in a random order at a rate of 120 bpm. Tissue Doppler imaging was carried out with GE VIVID 7 for off-line analysis at each pacing site. The global systolic contraction amplitude (GSCA) was calculated as the average shortening amplitude of all 16 segments of left ventricle.</p><p><b>RESULTS</b>The GSCA during pacing was 5.76 mm +/- 0.66 mm at free wall of RVOT and 5.66 mm +/- 1.00 mm at septum of RVOT, respectively. The GSCA at both sites was significantly higher than that at apical pacing 4.82 mm +/- 0.94 mm (P < 0.05) or low septum pacing 4.82 mm +/- 1.06 mm (P < 0.05). Moreover, segmental displacement analysis showed that the longitudinal displacement of lateral, posterior, and inferior walls significantly decreased at apical pacing compared with RVOT pacing, although no difference could be demonstrated in anterior and septum walls. Accordingly, the curve of the myocardial displacement at apical or low septum pacing was M-shaped, and had a negative wave at the end of the diastole in lateral, posterior, and inferior walls. The tissue velocity during isovolumic contraction period was also higher than systolic tissue velocity in these walls. The phenomenon could seldom be seen at RVOT pacing.</p><p><b>CONCLUSION</b>RVOT pacing in patients without structural heart disease is associated with more favorable immediate myocardial contraction and mechanical synchrony compared with right apical pacing or low septum pacing.</p>