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Aims: Simultaneous biventricular pacing improves left ventricular (LV) systolic performance in patients with dilated cardiomyopathy and intraventricular conduction delay. We tested the hypothesis that further improvements can be obtained using sequential biventricular pacing by optimizing both atrioventricular and interventricular delays., Methods and Results: In 12 patients, LV pressure, right ventricular (RV) pressure and respective rates of change of pressure (dP/dt) were acutely measured during biventricular pacing with different atrioventricular and interventricular (VVi) intervals ranging from -60 to +40 ms. The average increase vs. baseline in maximum LV dP/dt was higher for sequential than for simultaneous biventricular pacing (VDD mode: 35+/-20 vs. 29+/-18%, P<0.01; DDD mode: 38+/-23 vs. 34+/-25%, P<0.01), with a minority of patients accounting for most of the difference. The mean optimal VVi was -25+/-21 ms in VDD mode and -25+/-26 ms in DDD mode. With these settings, RV dP/dt was not significantly different from baseline. QRS shortening was not predictive of LV dP/dt increase., Conclusion: A significant increase of LV dP/dt with no change in RV dP/dt can be obtained by sequential biventricular pacing as compared to simultaneous biventricular pacing. The highest LV dP/dt is achieved when LV is stimulated before RV. The hemodynamic advantage might be of clinical significance in selected cases.

The aim of this study was to evaluate ventricular arrhythmias occurring in recipients of the InSync ICD for the primary and secondary prevention of sudden death. The InSync ICD was implanted in 142 patients (128 men; mean age 65 +/- 10 years) with heart failure (mean NYHA functional Class 3.0 +/- 0.7) and wide QRS (mean 159 +/- 33 ms). The underlying etiology was ischemic in 55%, idiopathic in 33%, and valvular or hypertensive cardiomyopathy in 12% of patients. The numbers of arrhythmic episodes/100 patient-months was computed with their 95% CI, assuming a Poisson distribution. Implants were performed in 48 (34%) patients who did not have an ACC/AHA guidelines Class I indication for ICD therapy. A total of 104 patients were compliant for follow-up visits. During a 9-month median (range 0.1-24) follow-up of 104 compliant patients, 19 experienced a total of 94 ventricular arrhythmias, all successfully interrupted or self-terminated, with a median number of two separate episodes, corresponding to a rate of 10 episodes/100 person-month (95% CI 8-12). A rate of 12 episodes/100 person-months (95% CI 10-15) was measured in the subgroup of patients with ACC/AHA class I indications, versus two episodes/100 person-months (95% CI 1-5) in the remainder of the population. Among 12 deaths, 9 were due to heart failure, 1 to a non-cardiovascular cause, and 2 to unknown causes. The implantation of ICD in heart failure patients has been prominently extended to primary prevention. Patients without standard ICD indications experienced life-threatening arrhythmic events. The impact of ICD combined with cardiac resynchronization therapy on arrhythmic profile, mortality, and costs in this subgroup of patients need to be more precisely studied, with a particular focus on the various types of underlying heart disease.

Unlabelled: 48 patients (40 Male), mean age 68 +/- 8 years, in III-IV class, with intraventricular conduction delay, received a biventricular pacemaker. Heart failure aetiology was non-ischemic in 60%. Left ventricular lead positioning was inferior in 5 patients (10%), posterior in 12 (25%), lateral in 18 (37%) and anterior in 13 (27%). QRS duration and axis were evaluated in sinus rhythm, and during right ventricular pacing, left ventricular pacing and biventricular pacing, the last early after implant and late after 8.8 +/- 4.3 months. QRS duration (ms) was 154 +/- 29 in sinus rhythm, 175 +/- 28 during right ventricular pacing, 196 +/- 31 during left ventricular pacing, 122 +/- 23 during biventricular pacing "early" and 120 +/- 18 during biventricular pacing "late." All the differences were statistically significant, but not between "early" and "late" biventricular pacing. Mean QRS axis ( degrees ) was -27 +/- 32 in sinus rhythm, -75 +/- 4 during right ventricular pacing, 112 +/- 41 during left ventricular pacing, -82 +/- 51 during biventricular pacing "early" and -80 +/- 42 during biventricular pacing "late." Only the difference between left ventricular pacing and all the other groups was statistically significant. QRS axis did not significantly differ according to left ventricular lead site during left and biventricular pacing. "Late" compared with "early" biventricular pacing axis showed variation >30 degrees in 35% of patients, in spite of no significant changes in QRS duration and x-ray positioning., Conclusion: Biventricular pacing significantly reduced QRS width, which persisted long-term. Left and biventricular pacing axis was poorly related to left ventricular lead positioning. Biventricular pacing axis variability over time may suggest a role of electrical remodeling.

Introduction: Biventricular pacing improves functional status in the majority of patients with drug-refractory heart failure, dilated cardiomyopathy, and interventricular conduction delay. The aim of this study was to analyze the baseline clinical and functional data of a cohort of patients implanted with a biventricular stimulation system in a single-center experience, to verify if the pathophysiologic characteristics of patients affect outcome, and to determine if preliminary identification of the right candidates for the new therapy is possible with noninvasive parameters., Methods and Results: Since March 1999, 52 patients with advanced heart failure (idiopathic cardiomyopathy 50%, ischemic cardiomyopathy 35%, other etiology 15%) and left bundle branch block underwent cardiac resynchronization and were followed prospectively. Paired analysis over mean (+/- SD) follow-up of 348 +/- 154 days showed an overall significant decrease of QRS width (baseline 194 +/- 33.2 msec vs follow-up 159.6 +/- 20.1 msec), New York Heart Association (NYHA) functional class (baseline 3.2 +/- 0.5 vs follow-up 2.3 +/- 0.5), quality-of-life score (baseline 54 +/- 25 vs follow-up 25 +/- 16), and increase of maximal VO2 (baseline 12.6 +/- 2.5 mL/kg/min vs follow-up 15.0 +/- 3.3 mL/kg/min). There were 80% responders (documented, persistent decrease > or = 1 NYHA class) and 20% nonresponders (same NYHA class or decline of status; need for heart transplant; death due to progressive pump failure). No significant differences in baseline clinical and functional variables between the two subgroups were observed. In responders, there was a highly significant global improvement of all variables; in nonresponders, no parameters changed between baseline and follow-up., Conclusion: These data confirm the role of biventricular pacing in improving the functional status of the great majority of a selected patient population having advanced heart failure and left bundle branch block with wide QRS complex. Basal demographic, clinical, and functional characteristics are not helpful in preliminary selection of responders. Simple evaluation of NYHA class confirms favorable outcome (improvement of functional and hemodynamic status).

Aim: A prospective randomized trial was set up to evaluate contractile parameters and quality of life in patients with congestive heart failure., Methods and Results: We describe the results from 38 patients in sinus rhythm and with chronic heart failure due to congestive cardiomyopathy, prospectively randomized to optimal medical therapy (Group 1, 19 patients) or optimal medical therapy plus dual chamber pacemaker programmed to optimal AV delay (Group 2, 19 patients). At a 6 month follow-up, 7/19 patients in Group 1 had died compared with 5/19 patients in Group 2. During follow-up, there were few significant changes in evaluated parameters except for mitral regurgitation time, which was prolonged in Group 1 and shortened in Group 2. The systolic left ventricular diameter shortened significantly only in Group 2. An energy and activity questionnaire showed that the effect of DDD pacing in the latter patient population was beneficial., Conclusions: From these results we may conclude that at the 6 month follow-up DDD pacing with echo-optimized AV interval programming can improve quality of life without affecting survival.

To evaluate the safety and efficacy of a new algorithm for automatic mode switching (AMS) from DDD-DDDR to DDIR, 26 patients, 16 females and 10 males, mean age 73 +/- 6 years of age, affected by sinus node disease, chronotropic incompetence, and recurrent paroxysmal atrial fibrillation (PAF) received the Medtronic Thera DR pacemaker. The device continuously calculates, in ms, the running average of the intrinsic atrial rate (MAR) and compares the current atrial interval (CAI) with the stored MAR. When the CAI is greater than the MAR it increases by 8 ms, and when the CAI is less than the MAR, it decreases by 23 ms. When MAR < or = 330 ms (182 beats/min), tachycardia is detected and AMS is activated. All patients had clinical evaluation, 12-lead ECG, Holter monitoring, and exercise testing after implantation and every 3 months for 1 year. The results were compared with the data stored in the pacemaker memory: AMS episodes number; the histogram of the last 14 episodes; and atrial electrogram recording. Twenty-two Holter recordings in 13 patients showed PAF and in all of them AMS occurred simultaneously. AMS lasted between 10 seconds and 20 hours, and MAR ranged from 195-400 beats/min. No episode of PAF and no AMS were recorded in 39 Holter recordings in 22 patients. Appropriate AMS was confirmed in five patients by stored atrial electrogram and in nine by 12-lead ECG and pacemaker event markers. Mean atrial sensing was 2.13 +/- 1.04 mV during PAF and 3.18 +/- 1.46 mV during sinus rhythm. No PAF episode and no AMS were recorded during exercise testing. In conclusion, this new algorithm was very reliable, sensitive, and specific.