Contractile Adaptations Preserving Cardiac Output Predispose the Hypertrophied Canine Heart to Delayed Afterdepolarization–Dependent Ventricular Arrhythmias
| Autor: | Mirella M C Molenschot, Hein J.J. Wellens, Jet D.M. Leunissen, Marc A. Vos, Marieke Schoenmakers, S. H. Marieke de Groot |
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| Rok vydání: | 2000 |
| Předmět: |
Male
Tachycardia Cardiac function curve medicine.medical_specialty Cardiac output Heart block Heart Ventricles Adaptation Biological Diastole Cardiomegaly Afterdepolarization Dogs Physiology (medical) Internal medicine medicine Animals Repolarization Cardiac Output business.industry Arrhythmias Cardiac medicine.disease Myocardial Contraction Disease Models Animal Heart Block Anesthesia Cardiology Female medicine.symptom Cardiology and Cardiovascular Medicine business Atrioventricular block |
| Zdroj: | Circulation. 102:2145-2151 |
| ISSN: | 1524-4539 0009-7322 |
| DOI: | 10.1161/01.cir.102.17.2145 |
| Popis: | Background —In dogs, chronic complete atrioventricular block (CAVB) results in structural (biventricular hypertrophy) and electrical (delayed repolarization) remodeling, which predisposes the heart to torsade de pointes arrhythmias. We assessed the contractile alterations in the CAVB dog and tested the hypothesis that these adaptations increase delayed afterdepolarization (DAD)–dependent triggered arrhythmias. Methods and Results —Steady-state and dynamic (fast pacing: 1 to 68 stimuli) left and right ventricular systolic and diastolic parameters were determined by positive and negative inotropic interventions at acute AVB and CAVB. Concomitantly, left and right ventricular endocardial monophasic action potentials were registered. In CAVB, all systolic contractile parameters were markedly increased, resulting in preserved cardiac output. The increase was most pronounced at low heart rates, altering the force-frequency response. At both acute AVB and CAVB, the degree of potentiation of cardiac function with pacing was dependent on the number of stimuli and showed a maximum at 8 to 13 stimuli. With CAVB, this potentiation curve was shifted upward, and it was only then that pacing resulted in DADs (in 8 of 10 dogs) and ectopic beats (EBs, in 6 of 10 dogs). The incidence of EBs in relation to the number of stimuli also had a maximum at 8 to 13 stimuli. Ouabain increased the incidence of DADs and EBs, whereas the negative inotropic interventions prevented them completely. Conclusions —The alterations responsible for improvement in systolic contractile function in CAVB dogs predispose the hypertrophied heart to DAD-dependent triggered arrhythmias during positive inotropic interventions. |
| Databáze: | OpenAIRE |
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