Prediction of vasovagal syncope from heart rate and blood pressure trend and variability: experience in 1,155 patients.

BACKGROUND: Vasovagal syncope (VVS) is a complex fainting disorder commonly triggered by orthostatic stress. OBJECTIVE: We developed an algorithm for VVS prediction based on the joint assessment of RR interval (RR) and systolic blood pressure (SBP). METHODS: Simultaneous analysis of RR and SBP trends during head-up tilt as well as their variability represented by low-frequency power (LFRR and LFSBP) generated a cumulative risk that was compared with a predetermined VVS risk threshold. When cumulative risk exceeded the threshold, an alert was generated. Prediction time was the duration between the first alert and syncope. In the first 180 sec of head-up tilt, baseline values were established, following which VVS prediction was possible. An analysis was performed using 1,155 patients who had undergone head-up tilt for syncope: 759 tilt-positive and 396 tilt-negative patients. In the tilt-test protocol, at syncope or after 35 min, the patient was returned to supine. RESULTS: In tilt-positive patients, VVS was predicted in 719 of 759 patients (sensitivity 95%), whereas 29 false alarms were generated in 396 tilt-negative patients (specificity 93%). Prediction times varied from 0 to 30 min but were longer than 1 min in 49% of patients. CONCLUSION: Predicting impending syncope requires use of simultaneous blood pressure and heart rate, which may shorten diagnostic testing time, free patients from experiencing syncope during a diagnostic tilt-test, and have application in risk-guided tilt training and in an implanted device-to-trigger pacing intervention. The prospects for relieving patient discomfort are encouraging.

Reducing ventricular pacing in sinus node dysfunction.

BACKGROUND: The use of DDIR mode has been limited since the advent of mode switch in the DDDR mode. In patients with AV block, DDDR is necessary to maintain AV synchrony. However, DDIR mode may still be beneficial for patients with intact AV conduction. The aim of this study was to compare the incidence of ventricular pacing and atrial tachyarrhythmia in DDIR and DDDR with mode switch in a randomized, single-blind, crossover study, and discuss the utility of both modes. METHODS AND RESULTS: Twenty-four patients (8 males) with bradycardia-tachycardia syndrome and no signs of AV block (mean age 70.1 +/- -9.1 years) were enrolled and randomized to DDIR or DDDR modes with the leads placed at the right atrial appendage and right ventricular apex. After 12 weeks, patients were switched to the opposite mode. During the study period, atrial high rate episodes and other pacemaker diagnostic data were collected. Significantly less ventricular pacing was observed in DDIR mode (DDIR versus DDDR; 48.9%, 76.5%, P = 0.0002) and atrial high rate episodes were significantly lower in DDIR mode (DDIR versus DDDR; 1.32, 1.85 per day, P < 0.05). CONCLUSION: In patients with sinus node dysfunction and intact AV conduction, DDIR mode may have important implications for simplifying device programming, device longevity, and to avoid atrial tachyarrhythmia.

Nocturnal overdrive pacing for the treatment of sleep apnea syndrome.

STUDY OBJECTIVES: We investigated the effect of 1 week of nocturnal overdrive pacing (NOP) on the apnea-hypopnea index (AHI) in patients with a chronically implanted pacemaker and diagnosed during a screening phase with sleep apnea. DESIGN: Randomized, single-blind, crossover study. SETTING: University medical centers in Zürich, Switzerland, and Berlin, Germany. PATIENTS: Nineteen patients with mild to severe sleep apnea/hypopnea (16 men, mean age = 68.8 +/- 11.4 years) participated. The individuals did not suffer from permanent atrial arrhythmia, did not use continuous positive airway pressure, and had been implanted with atrial or dual-chamber pacemakers. INTERVENTIONS: Nocturnal lower rates were 45 and 75 beats per minute (bpm) at night for the control and NOP arms, respectively, and daytime lower rates were 60 bpm. Subjects were in each arm for 1 week. MEASUREMENTS AND RESULTS: Heart-rate increase from control (61 +/- 9 bpm) to NOP (78 +/- 4 bpm) followed by significant reduction in circulation time (24.6 seconds control, 20.7 seconds NOP; p = .04) resulted in no significant change in AHI (26.8 +/- 17.1/h control, 23.0 +/- 16.7/h NOP; p = .49). Seven subjects characterized by a higher hypopnea index, less stage 1 and 2 sleep, and less slow-wave sleep improved at least 1 AHI severity level with NOP, mainly attributable to reduction of hypopneas. CONCLUSION: NOP over a period of 1 week followed by a reduction in circulation time did not improve AHI in patients with SA. Whether an improvement by 1 AHI severity level in a specific subset of patients reflects a true response remains to be elucidated by further studies.

Physiologic pacing in patients with obstructive sleep apnea: a prospective, randomized crossover trial.

OBJECTIVES: This study was designed to assess the impact of prevention of bradycardia with physiologic pacing on the severity of obstructive sleep apnea. BACKGROUND: Apneic episodes during sleep are associated with slowing of the heart rate during apnea and tachycardia with subsequent arousal. Patients with permanent pacemakers may have reduced episodes of sleep apnea when their pacemaker rate is set faster than their spontaneous nocturnal heart rate. METHODS: We conducted a prospective, randomized, single-blind crossover trial of temporary atrial pacing in obstructive sleep apnea to reduce the apnea hypopnea index (AHI). Fifteen patients (age 60 +/- 13 years, 12 men) with moderate to severe obstructive sleep apnea (AHI 34 +/- 14) underwent insertion of an externalized atrial permanent pacing system via the left subclavian vein. Patients underwent overnight respiratory sleep studies in hospital, during atrial pacing at 75 beats/min, and with pacing turned off. The order of pacing mode was randomized, with crossover the subsequent night to the other mode. Patients were blinded to pacing mode, and the analysis of sleep recordings was blind to pacing mode. RESULTS: Pacing was tolerated without complications in all patients. Overnight physiologic pacing did not affect the AHI (pacing 39 +/- 21/h vs. control 42 +/- 21/h, p = 0.23, 95% confidence interval -9.3 to 2.5 for difference), desaturation time (pacing 3.8 +/- 6.0% vs. control 3.5 +/- 4.3%, p = 0.70), or the minimum SaO(2) (pacing 75 +/- 10% vs. control 77 +/- 11%, p = 0.38). There was a borderline significant reduction in circulatory time with pacing (pacing 23.4 +/- 3.2 s vs. control 25.5 +/- 4.4 s, p = 0.09). CONCLUSIONS: Temporary atrial pacing does not appear to improve respiratory manifestations of obstructive sleep apnea. Permanent atrial pacing in this patient population does not appear to be justified.

Effects of ventricular rate regularization pacing on quality of life and symptoms in patients with atrial fibrillation (Atrial fibrillation symptoms mediated by pacing to mean rates [AF SYMPTOMS study]).

The aim of this study was to investigate the effect of the Ventricular Response Pacing (VRP) algorithm, which regularizes ventricular rate during atrial fibrillation (AF), on symptoms, quality of life, and functional capacity. VRP regularizes the ventricular rate during AF without increasing the mean ventricular rate, thereby reducing the severity of AF-related symptoms in patients with persistent AF. However, VRP did not improve general quality of life (Medical Outcomes Study 36-item Short-Form General Health Survey), the performance of routine activities (Duke Activity Status Index), or functional capacity (hall walk) in patients with AF.