Single-chamber Versus Dual-chamber Implantable Cardioverter Defibrillators: Do We Need Physiologic Pacing in The Course?

BACKGROUND: Many patients with ICD receive different antiarrhythmic drugs (e.g. sotalol, amiodarone, β-blockers) because of ventricular or atrial tachycardias. These drugs can cause AV-block or chronotropic incompetence resulting in a higher percentage of ventricular pacing. METHODS: We analyzed in a retrospective study the impact of DDD(R) versus VVI(R) mode on subjective (NYHA classification) and objective parameters [brain natriuretic peptide (BNP), 6 minute walk test, echocardiography] in 12 of 120 patients (age 60.2 ± 11.2 years; 10 males, 2 females) who needed an upgrading of a single to a dual chamber ICD. The ICD had to be upgraded because of chronotropic incompetence in all patients with signs of progressing heart failure. Data were collected in VVI(R)-pacing and after 6 and 12 months in DDD(R)-pacing with a long AV-interval and AV hysteresis to reduce ventricular pacing. RESULTS: The 6 minute walk test (392.4 ± 91.4 vs. 324.6 ± 93.3 m, P < 0.001), NYHA-classification (1.4 ± 0.3 vs. 2.6 ± 0.8, P < 0.0001), BNP (234.1 ± 73.5 vs. 410.4 ± 297.0 pg/ml, P < 0.001), left ventricular ejection fraction (49.8 ± 9.6 vs. 36.5 ± 10.9 %, P < 0.0001) and A-wave (73.6 ± 13.7 vs. 41.0 ± 14.0 cm/sec, P < 0.0001) improved with DDD(R)-pacing after 12 months. The ventricular pacing decreased (84.2 ± 18.1 vs. 1.1 ± 1.7 %, P < 0.0001) after 12 months by DDD(R)-pacing with long AV-interval (220.0 ± 10.4 ms) and AV hysteresis. CONCLUSION: Our data show a superiority of DDD(R) mode versus VVI(R) mode regarding subjective and objective parameters as NYHA-classification, BNP, 6 minute walk test, left ventricular ejection fraction and left ventricular endsystolic volume after 12 months. The improvements seem to depend on the reduction of ventricular pacing with advanced atrial contraction. But only a small number of patients needed the upgradation.