MENOZZI, C., ET AL.: Intrapatient Comparison Between Chronic VVIR and DDD Pacing in Patients Affected by High Degree AV Block Without Heart Failure. In patients affected by high degree AV block without preexisting congestive heart failure there is no definite demonstration that DDD pacing gives real clinical advantages in respect to VVIR pacing. We performed an intrapatient, long-term study between the two pacing modes in 14 high degree AV block patients, using the Medtronic Synergyst 7027 dual chamber pacemaker, who could be programmed alternatively in DDD or VVIR mode. After a 4-week run-in period following the pacemaker implant, patients completed a randomized, double-blind, cross-over study to compare the effect of 6-week period VVIR and DDD pacing on symptoms and cardiovascular parameters. A semiquantitative score scale was used to quantify the symptoms of general well-being, palpitations, dizziness, pulsating sensation in the neck or abdomen, shortness of breath at rest and during effort, chest pain, and NYHA classification. The sum of symptom scores was 10.4 ± 6.7 in VVIR period and 4.6 ± 2.7 in DDD period (p < 0.001); five patients (36%) crossed over early from VVIR to DDD because of intolerable symptoms; overall, eight patients preferred the DDD mode and no one preferred the VVIR. Cardiac output at rest (echo-Doppler method) was 4.7 ± 1.4 versus 5.7 ± 1.6 liter/min (p < 0.01), body weight was 65.9 ± 6.6 versus 64.9 ± 6.1 kg (p < 0.02), atrial natriuretic peptide was 236 ± 112 versus 198 ± 110 pg/mL (p < 0.01), respectively, during VVIR and DDD modes. Effort tolerance was similar with the two modes of pacing (68 ± 15 vs 70 ± 18 watt/min). In conclusion, hemodynamic advantages of atrial synchronization reflect a better quality of life for the patients even if an individual variability exists.