Global Dispersion Of Ventricular Repolarization Under Heart Failure And Different Ventricular Pacing Protocols In Vivo

Part one（1） Global Dispersion of Ventricular Repolarization with Pacing at Difference Sites in Health SwineObjective: Epicardial pacing may lead to a prominent increase in transmural dispersion, which may be linked to the reported malignant ventricular arrhythmias. We study the global dispersion of ventricular repolarization under different sites pacing in vivo.Methods: Using the CARTO system, monophasic action potential （MAP） mapping of the left and right ventricular endocardium was performed during right atrial （RA） pacing, right ventricular apical endocardial (RV_Endo) pacing and left ventricular lateral epicardial (LV_Epi) pacing in 10 healthy pigs. Global dispersion of the activation time （AT） and end of repolarization time （EOR） were calculated as the maximal differences of these 2 parameters in each map. Recording the 12 leads electrocardiogram, Tpeak-Tend intervals（Tpe）, average Tpeak-Tend intervals （Tpe-AVE）, maximum Tpeak-Tend intervals （Tpe-MAX）, QT inteval and QT dispersion （QTd） were measured during RA pacing, RV_Endo pacing and LV_Epi pacing respectively in 10 healthy swines.Results:1. The MAPd was no significant during RA and RV_Endo pacing （p > 0.05）. The MAPd of left and right ventricle during LV_Epi pacing were significantly greater compare those during RV_Endo pacing（both p<0.05）.2. The AT dispersion of left ventricle, right ventricle and bi-ventricle during RV_Endo pacing was greater than those during RA （all p<0.05）. The AT dispersion was similar between LV_Epi and RV_Endo pacing（p>0.05）. The AT dispersion of bi-ventricle during LV_Epi pacing increased comparing with RV_Endo pacing（p<0.05）.3. The global dispersion of EOR times during LV_Epi pacing （94±17 ms） was significantly greater than those during RA （63±12 ms, p < 0.05） and RV_Endo pacing （72±18 ms, p < 0.05）, whereas no significant difference was found between those during RA and RV_Endo pacing （p > 0.05）.4. QT interval during LV_Epi pacing （328±24 ms） was significantly greater than that during RA pacing （295±13 ms, p< 0.05） and RV_Endo pacing （304±17 ms, p<0.05）, whereas no significant difference was found between that during RA and RV_Endo pacing. QT dispersion during LV_Epi pacing （33±6 ms） appeared significantly greater than that during RA （17±3 ms, p< 0.05） and RV_Endo pacing （18±3 ms, p<0.05）. No significant difference in QT dispersion was found during RA pacing and RV_Endo pacing （p>0.05）. During RA pacing, the Tpe-AVE and Tpe-MAX were 49±6 ms and 58±8 ms, which were similar to those during RV_Endo pacing （49±8 ms and 60±8 ms, both p>0.05）. However, during LV_Epi pacing, Tpe-AVE and Tpe-MAX increased significantly to 63±7 ms and 71±8 ms (both p< 0.05 comparing with RA and RV_Endo pacing ).Conclusion: Compared to RA and RV_Endo pacing, LV_Epi pacing increases the global dispersion of ventricular repolarization in health swine.（2） Global Dispersion Of Ventricular Repolarization Under Different Ventricular Pacing Protoclos: Monophasic Action Potential Mapping Using CARTO System In DogsObjective: Increased dispersion of ventricular repolarization （DVR） is associated with the ventricular tachyarrhythmias （VTA）, which may be one of major reasons for sudden death in heart failure （HF）. Cardiac resynchronize tion therapy （CRT） has been widely used recently for HF patients. However, it is still lack of the knowledge of the DVR in HF, especially under different pacing situations. This study is to investigate the changes of global DVR under different pacing protocols in canine congestive HF models.Methods: Using the CARTO system, in vivo monophasic action potential （MAP） mapping of the left and right ventricular endocardium was performed during RA pacing, RV apical endocardial (RV_Endo) pacing, LV lateral epicardial (LV_Epi) pacing and bi-ventricular （Biv） pacing in 6 dogs before and after the induction of congestive HF. The dogs with HF were induced by RV (240 bpm rapid pacing for 4 to 5 weeks, and then 190bpm for 4 weeks. Global dispersion of the activation time （AT） and end of repolarization time （EOR） were calculated as the maximal differences of these 2 parameters in each map. The 12 leads ECG was simultaneously recorded during the global ventricular MAP mapping.Results:1. Before and after induction of HF, the AT and EOR during RV_Endo pacing, LV_Epi pacing and Biv pacing was significantly increased than that during RA pacing （all p<0.05）.2. The global DVR during LV_Epi pacing is most big in the 4 kind of pacings for control group （all p<0.05）. AT dispersion and EOR dispersion during LV_Epi pacing are similary with that during RV_Endo pacing in HF group （both p>0.05）.3. The global DVR in HF group is even more than that of control group during RV_Endo pacing （p<0.05）.Conclusions:1. The global DVR during LV_Epi pacing is most great comparing other pacings in control group.2. The global DVR of dogs with HF was significantly increased than that of dogs without HF during 4 kinds of pacing. The dogs with high global DVR maybe suffer from more VTA.3. The global DVR during RV_Endo pacing is greater than that of LV_Epi pacing, although LV_Epi pacing resuts in high global DVR in HF group.4. The global DVR decrease during Biv pacing and Biv pacing maybe reduce VTA. Part twoTransmural Gradient of Repolarization Under Different Ventricular Pacing Protocols: Monophasic Action Potential Mapping on Left Ventricle for Heart Failure dogs in VivoObjective: Alterations of transmural gradient of repolarization may contribute to increase the transmural dispersion of repolarization and ventricular arrthymias. The change of transmyocardial activation sequences and gradient of repolarization maybe play an important role in sudden death by different ventricular pacing. We study transmural gradient of repolarization in the failing and nonfailing dog hearts under different ventricular pacing mode.Methods: Mongrel dogs（n=8） were randomized into two groups:dogs in the control group （n=4） were nonfailing dogs.Dogs in heart failure group （n=4） were the congestive heart failure （CHF） models induced by fast ventricular rapid pacing （240 bpm for 4 to 5 weeks）.Through a median sternotomy, the pericardium was opened with a base-to-apex incision. The tip of a bipolar-pacing catheter was positioned in the RV apex via the right external jugular vein under fluoroscopic guidance. Epicardial lead （Medtronic 4965） was sutured on the posterior-lateral region of the left ventricle. In both normal and models with CHF mongrel dogs, monophasic action potential duration （MAPd） of subendocardial, subepicardial and mid-layer myocardium were recorded in the ten points of left ventricle during sinus rate, pacing from endocardium of RV apex (RV_Endo), epicardium of LV anterior wall (LV_Epi)and biventricle （Biv） simultaneously. The MAPd data were corrected by BaZett’s formulae.Results:1. In health dog, the MAPd was longest in mid-layer myocardium and shortest in subepicardial layer, there are significant difference in subendocardial, subepicardial and mid-layer myocardium during sinus rate （p<0.05）. The MAPd was longer in mid-layer myocardium comparing subepicardial layer during RVendo, LV_Epi and Biv pacing（p<0.05）, but the MAPD of subendocardial and subepicardial layer was resemble （p﹥0.05）.2. The MAPd in subendocardial, subepieardial and mid-layer were prolonged respectively after heart failure （comparing with control group, p<0.05）.3. In the CHF group dogs, the MAPd was longest in mid-layer myocardium and shortest in subepicardial layer still, but there were no difference in three-layer myocardium during sinus rate （p﹥0.05） and similar during RV_Endo, LV_Epi and Biv pacing （p﹥0.05）.Conclusions:1. The transmural MAPd gradient was recorded during subendocardial, subepicardial and mid-layer myocardium in the health dog, the transmural gradient reduce after heart failure.2. Different pacing results in the heterogeneous prolongation of transmural MAPd between health and CHF dog. The MAPd in subepicardial layer was prolonged maximally in health dog, but prolonged uniformly in CHF dog.Part threeThe Evaluation of Global Dispersion of Ventricular Repolarization in Dilated Cardiomyopathy Patients with Heart Failure by the Characteristic of ElectrocardiogramObjective: The malignant ventricular tachyarrhythmia increase in patient suffering from HF and maybe relate to transmural dispersion of ventricular repolarization after HF. This study aimed to evaluate the characteristics of the Tpe in patients with and without DCM.Method: Fifty three inpatients were enrolled in this study, which includes 28 patients with primary DCM and heart failure （male 15, aged 28⁵8, 45.3±6.14 ys; group DCM）, and 25 without structural heart disease （male 15, aged 21⁵1, 37.61±5.51 ys; control group）. The Tpe and the dispersion of QT interval（QTd） from the 12-lead surface ECG were acquired and measured mannually, and consequently the corrected numerals of the average of Tpe, the maximal Tpe. The corrected numerals and QT interval were then compared between the group of DCM and control.Results: The comparison between the group of DCM and Control: In group of DCM, the Tpe-AVEC, Tpe-MAXC and QTd were all significantly greater than those of control of group, which were 106.31±26.34 vs. 82.72±10.01 （P=0.027）, 234.05±69.75 vs. 119.15±11.55 （P<0.001）, 119.17±67.62 vs. 39.74±17.04 （P=0.01）, respectively.Conclusion: The global dispersion of repolarization were significantly increased in DCM with heart failure. The Tpe-AVEC and Tpe-MAXC are recommended to be used for evaluation of the ventricular repolarization dispersion as the prognostic index in patients with DCM and heart failure.