Study Of Ventricular Arrhythmias Induced By Cytomegalovirus Infection And Effects Of Radiofrequency Ablation On These Arrhythmias

Part IEvaluation of myocarditis and cardiac arrhythmias induced by murine cytomegalovirus and their mechanismsBacground Lack of study of murine cardiac arrhythmias induced by cytomegalovirus Objective To evaluate the myocarditis and the cardiac arrhythmias induced by murine cytomegalovirus and to investigate their mechanisms.Methods sixty male four weeks Balb/c mice were random divided into two groups: one was experiment group (A group, abdominal injection of murine cytomegalovirus) and control group (B group, abdominal injection of 3T3 liquid). At 3,7,14,21,28,35,42,49,56,63 and 70 day after cytomegalovirus infection, blood taken from canthus vessels was used to detect serum antibodies against myocardial β₁ receptor. Meantime, electrocardiographies of mice were recorded. After killing mice, getting out their hearts, tested gene express of murine cytomegalovirus, took pathological examination and immunohistochemical examination. After separating ventricular muscle cells of mice, tested effects of above antibodies against myocardial β₁ receptor on acting potential duration and L-type Ca²⁺ currents,under condition of current clamp and potential clamp. And then detected intracellular Ca²⁺ concentration of murine cardiac myocytes by laser confocal technique.Results Total incidence of myocarditis of BALB/c mice in experiment group was 69.4% at 70 day after cytomegalovirus infection. Total mortality was 11.1% in this group at end of the experiment. There wasn't one murine died in another control group. Microscopical pathology showed that changes of myocardium pathologically were obvious in experiment group from 7day to 14 day after the virus infection. The main pathological changes were that some myocytes were swelling and denaturalization, other single myocyte was necrosis, and inflammatory cells infiltrated in myocardial tissue in a focus and dispersed fashion. Even if at 70 day after the virus infection, inflammatory cells still infiltrated in heart tissue dispersedly. Half quantitative analysis by pathology showed that the myocarditis induced by cytomegalovirus was mild. Result of immunohistochemistry showed that strong expression of proteins of cytokin IL-1β and TNF-α in myocardium at 3-7 day after the virus infection. In experiment group, gene of cytomegalovirus was deteced at 3-7 day after virus infection, and was undetectable from 14 day to 70 day after virus infection. Whereas, gene of cytomegalovirus was undetected at all the time in control group. From 1 to 7 weeks after virus infection, the anti-cardiac β₁ receptor autoantibody titer of sera in control group were zero, but mild elevation from 8 to 10 weeks. The anti-cardiac β₁ receptor autoantibody titer of sera were zero at former 5 weeks after virus infection and were significantly high elevation at latter 5 weeks after virus infection. Total incidences of cardiac arrhythmias were about 50% in A group. Most of cardiac arrhythmias were sinus arrhythmias, atrial arrhythmias and conduction black at the former 5 weeks, and were ventricular arrhythmias and atrial arrhythmias at the latter 5 weeks in A group. After separating ventricular muscle cells of mice, prolongations of acting potential duration of cardiomyocytes were observed when adding anti-cardiac β₁ receptor autoantibody diluted at 1:100 to incubation liquid, but this phenomenon were not found if adding metoprolol to incubation liquid beforehand. Autoantibodies against β₁-adrenoceptor diluted at 1:100 significantly increased the I_Ca-L peak current amplitude and elevation of intracellular Ca²⁺ fluorescent intensity. Wheres, blocking of β₁-adrenoceptor by metoprolol beforehand, autoantibodies against β₁-adrenoceptor diluted at 1:100 induced a slight increase of I_Ca-L peak current amplitude and mild elevation of intracellular Ca²⁺ fluorescent intensity.Conclusion Murine cytomegalovirus can cause acute and chronic myocarditis, even more induce various cardiac arrhythmias in BALB/c mice. The pathologicall changes of myocardium and arrhythmias are related with cytomegalovirus infection at early period of the virus infection, but may be related with autoantibodies against β ₁-adrenoceptor at chronic period. Autoantibodies against β₁-adrenoceptor may lead ventricular arrhythmias by increasing I_Ca-L current and elevation of intracellular Ca²⁺ concentration.Part IICorrelation between viral infection, idiopathic right ventriculararrhythmias and its morphological abnormalities of rightventricle delineated by MRIBackground The etiology of idiopathic right ventricular arrhythmias (IRVA) isunknown.Objective To evaluate correlation between viral infection, IRVA and itsmorphological abnormalities of right ventricle delineated by magnetic resonanceimaging(MRI) in patients with IRVA.Methods Case control study was performed. All subjects were divided into fourgroups: IRVA group, idiopathic left ventricular tachycardia (ILVT) group, othercardiovascular diseases control (Heart-Disease-Control) group and healthy controlgroup. IRVA group had fourty-five patients; fifty subjects were in each of other three groups. All these four groups were age- and sex- matched. Every subject underwent baseline tests, including electrocardiogram, X-ray chest, transthoracic echocardiography, etc, on routine basis. Then all of these subjects went through more tests, including viral serology, MRI, serum cardiac autoantibodies, the mark of damage of myocardium, etc. The subjects in IRVA group, in ILVT group and in Heart-Disease-Control group were follow-up in 6-12 months.Results MRI revealed right ventricular wall structural abnormalities more often inIRVA group (31 [68.9%] of 45) than in ILVT group (3[6%] of 50, p<0.01), inHeart-Disease-Control group (5[10%] of 50, p<0.01) and in healthy control group(6[12%] of 50, p<0.01). These structural abnormalities included fixed focal wallthinning, fatty deposits, small saccular aneurysm, etc. The positive rates of serum IgMantibodies against Coxsackie B virus were low in each of these four groups (amongthe four groups, p>0.05). But the positive rates of serum IgM antibodies againstcytomegalovirus were markedly higher in IRVA group (33[73.3%] of 45) than in otherthree groups (6[12.0%] of 50, 4[8.0%] of 50 and 7[14.0%] of 30; IRVA group vs otherthree groups, p<0.01). After 6-12 months follow-up, the positive rates of serum IgMantibodies against cytomegalovirus in IRVA group (30 [66.7%] of 45) kept high, too.Analysis of correlation found intensities of correlation between Coxsackie B virusinfection, IRVA and its right ventricular wall structural abnormalities werelow(p>0.05), but intensities of correlation between cytomegalovirus infection, IRVAand its right ventricular wall structural abnormalities were high(p<0.001). Serumlevels of the mark of damage of myocardium (including creatine kinase, creatinekinase-MB, and cardiac-specific troponin-I) were in normal ranges in all of thesegroups(p>0.05). Among four common cardiac autoantibodies, the positive rates ofautoantibody against β₁ adrenergic receptor were higher in IRVA group than in otherthree groups(IRVA group vs other three groups, p<0.01). But the positive rates ofother three autoantibodies were low in each of these four groups (among four groups,p>0.05).Conclusion The positive rates of cytomegalovirus infection are high in patients with IRVA. Focal structural abnormalities of right ventricular wall occur more often in these patients. Cytomegalovirus infection is correlated with occurrences of IRVA and its right ventricular wall structural abnormalities in IRVA patients. Cytomegalovirus infection may be the cause of IRVA. Effects of cytomegalovirus may be partly mediated by autoantibodies against β₁ adrenergic receptor.Part IIIEffects of radiofrequency ablation on idiopathic rightventricular arrhythmias accompanied with persistentcytomegalovirus infectionBackground Radiofrequency catheter ablation (RFCA) has been used widely for treatment of tachyarrhythmias for many years.Objective To explore effects of RFCA on idiopathic right ventricular arrhythmias (IRVA) accompanied with persistent cytomegalovirus infection. Methods Forty-five patients with IRVA were involved in this study. These patients meted with selecting criterion of IRVA. Before ablation, all patients received routine tests, including electrocardiography, X-ray chest, transthoracic echocardiography, etc. Then all of these patients went through more tests, including cytomegalovirus serology, MRI, serum cardiac autoantibodies, the mark of damage of myocardium and intracardiac electrophysiology, etc. All patients were follow-up in 6-12 months, and then received some tests again, including tests of cytomegalovirus serology and serum cardiac autoantibodies.Results These forty-five patients detected serum IgM antibodies against cytomegalovirus. Among these patients, thirty-three patients (33/45, 73.3%) before ablation and thirty patients (30/45, 66.7%) after ablation 6-12 moonth follow-up were positive of the antibodies in serum. MRI revealed right ventricular wall structural abnormalities found in thirty-one patients (31 [68.9%] of 45). These structural abnormalities included fixed focal wall thinning, fatty deposits, small saccular aneurysm, etc. Positions of the right ventricular structural abnormalities were not related with origins of IRVA. Among four serum autoantibodies, only positives of autoantibodies against β₁ adrenergic receptor were high (62.2%), wheres the positives of other three autoantibodies were low. After follow-up, the positives of autoantibodies against β₁ adrenergic receptor kept high too (64.4%). In patients with positive IgM antibodies against cytomegalovirus, most of them were positive of autoantibodies against β₁ adrenergic receptor (25/33 , 75.8%). Intracardiac electrophysiology showed, thirty-five patients (35/45, 77.8%) had spontaneously IRVA, which configuration of QRS waves were same with that of usually time. Outbreak of IRVA in other nine patients (9/45, 20%) need infusion of epinephrine. IRVA were not induced in one patient (1/45, 2.2%) and ablation was abandoned. Among the forty-four patients received ablation, RFCA was success in forty-three patients (43/44, 97.7%) immediately after RFCA. One patient stoped ablation as strong chest pain. After 6-12 moonth follow-up, there were reoccurrents in five patients (5/44, 11.4%), but second ablation was success. The total rates of success were 95.6% (43/45). In thirty-three patients with positive IgM antibodies against cytomegalovirus, thirty-one (31/33, 93.9%) patients had success of RFCA. Among twenty-eight patients with positive autoantibodies against β₁ adrenergic receptor, RFCA was success in twenty-seven patients (27/28, 96.4%).Conclusion RFCA is effect on IRVA in IRVA patients accompanied with persistent cytomegalovirus infection and positive serum autoantibodies against β₁ adrenergic receptor.