Efficacy of consistent atrial pacing algorithm for suppression of atrial arrhythmias in patients with sick sinus syndrome and atrial fibrillation.

Atrial overdrive provides the best opportunity to suppress atrial arrhythmias. Atrial preference pacing (APP) algorithm has been designed to achieve a high percentage of atrial pacing. The aim of this study was to assess the efficacy of APP algorithm in patients with implanted pacemakers and tachycardia-bradycardia syndrome. The subjects were 17 patients (mean age, 71.7+/-9.0 years old, 4 males) implanted with a DDDR pacemaker Thera DR (Medtronic, Minneapolis, MN, USA). All patients had sick sinus syndrome and paroxysmal atrial fibrillation before pacemaker implantation. Informed consent was obtained from each participant before enrollment. DDDR and mode switch or APP were randomly programmed. After two weeks, the pacing mode was switched to another mode. The percentage of atrial pacing was significantly higher in APP than in DDDR (97.7+/-1.4 versus 52.3+/-30.8, P<0.0001). Atrial premature beat counts were significantly greater in DDDR than in APP (30689+/-42534 versus 7717+/-10700, P<0.005). There was no significant difference in mode switch episode counts between DDIR and APP (2.6+/-5.5 versus 8.4+/-19.2, NS). Although there was no significant difference in mode switch episode counts between DDDR and APP, APP algorithm can successfully prevent atrial premature beats in patients with tachycardia-bradycardia syndrome.

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.

Reverse perfusion-metabolism mismatch predicts good prognosis in patients undergoing cardiac resynchronization therapy: a pilot study.

BACKGROUND: Cardiac resynchronization therapy (CRT) improves glucose metabolism in the septum of patients with heart failure, so in the present study the predictive value of combined fluorodeoxyglucose (FDG)-positron emission tomography (PET) and metoxy-isobutyl isonitrile (MIBI)-single photon emission computed tomography (SPECT) for the prognosis of patients undergoing CRT was investigated. METHODS AND RESULTS: Fourteen patients (70.3+/-8.2 years) who underwent FDG-PET and MIBI-SPECT before implantation of a biventricular pacemaker were enrolled. The total number of matches, mismatches, reverse mismatches, summed difference score (SDS: sum total of FDG - MIBI scores) and SDS per segment (%SDS) in each of 5 areas of myocardium (septum, anterior, lateral, inferior area, apex) was calculated and compared between the survival groups (all survival: survival group; survival without ischemic heart disease (IHD): non-IHD survival group) and non-survival group. Both the number of reverse mismatch segments and the %SDS in the septum in the non-IHD survival group were significantly greater than in the non-survival group (3.2+/-1.6 vs 0.5+/-0.6, p<0.05; 0.62+/-0.61 vs -0.11+/-0.19, p<0.05). The receiver-operating characteristics curves for prognosis showed that the area under the curve for the number of reverse mismatch segments in the septum (0.93; confidence interval 0.61-0.98) was significantly greater. CONCLUSION: A reverse mismatch pattern in the septum can predict a good prognosis for patients treated with CRT.

Suppression of atrial fibrillation by atrial pacing.

BACKGROUND: Atrial fibrillation (AF) is a common arrhythmia in patients with an implanted pacemaker, but the role of atrial pacing in preventing AF is still unclear. METHODS AND RESULTS: Sixty-six patients (67.8+/-12.1 years) were enrolled: 54 with sick sinus syndrome (SSS), 11 with atrioventricular blocks (AVB), and 1 with SSS and AVB. The prevalence of AF was investigated. In 22 patients with AF, the AF burden was estimated under "back-up pacing" (40-50 beats/min), then under "atrial pacing" (60-85 beats/min). The prevalence of AF in the SSS group tended to be higher than that in the AVB group (48.1% vs 18.2%, p=0.06). The AF burden in patients with a percentage of atrial pacing (% atrial pacing) <50% was significantly greater than that in patients with % atrial pacing >or=50% (12.5+/-21.1% vs 4.2+/-10.3%, p<0.05). AF disappeared immediately after "atrial pacing" in 4 patients (18.2%). In 9 patients (40.9%), the AF burden decreased gradually, and AF disappeared in 6 patients (27.3%) after 207.9+/-130.2 days. CONCLUSION: The prevalence of AF may be higher in patients with SSS than in those with AVB. Atrial pacing has a preventive effect on AF, and the effect of atrial pacing is not always immediate but is progressive in some patients.

Daily shock impedance measured by implantable cardioverter defibrillator is useful in the management of congestive heart failure.

BACKGROUND: Clinical data suggest that changes in intrathoracic impedance and fluid accumulation in the lung are inversely related. METHODS AND RESULTS: Daily shock impedance (S-IMP) was evaluated in 29 patients in whom a Ventak Prizm 2 was implanted (61+/-14 years old). The mean follow-up period was 45+/-18 weeks, during which 6 patients had episodes of decompensated heart failure (DHF group) and the others did not (NHF group). There was no significant difference between the DHF group and NHF group in the mean value of the S-IMP (46.4 +/-3.3 vs 45.4+/-5.4 Omega). The range of S-IMP in individual patients in the DHF group was significantly greater than that in the NHF group (13.8+/-0.38 vs 7.0+/-3.1 Omega, p<0.0001). Mean weekly change of S-IMP in individual patients in the DHF group was significantly greater than that in the NHF group (1.583+/-0.630 vs 1.092+/-0.361 Omega, p<0.0176). When the cut-off value was set at >1.242 Omega, sensitivity was 100% and specificity was 69.6% for a diagnosis of DHF. There was a significant negative correlation between the percent increases in brain natriuretic peptide (BNP) and S-IMP (correlation coefficient: -0.775 p<0.0001) in the DHF group. There was an inverse relation between BNP and S-IMP. CONCLUSIONS: Measurement of shock impedance may be useful in the management of congestive heart failure.

[Improvement of central sleep disordered breathing with severe congestive heart failure by biventricular pacing therapy: a case report].

A 74-year-old man with ischemic cardiomyopathy was repeatedly admitted for congestive heart failure. His left ventricular ejection fraction was 21% and diastolic left ventricular dimension was 73.5mm by echocardiography. He was treated with biventricular pacing and heart failure improved from New York Heart Association class III to II. Before the treatment, brain natriuretic peptide was 600.5 pg/ml. Apnea hypopnea index was 23.8 and all events were central type. After biventricular pacing, apnea hypopnea index was improved to 21.9 after 11 days, 14.0 after 33 days, and 4.8 after 48 days. His left ventricular ejection fraction was 36%, diastolic left ventricular dimension was 71.4mm, and brain natriuretic peptide was 383.8 pg/ml. In this patient, central sleep disordered breathing was improved by biventricular pacing therapy after only 48 days.

[Neurally mediated syncope with significant cardiac arrest and asymptomatic multiple cerebral infarctions: a case report].

A 32-year-old man had suffered episodes of loss of consciousness since childhood. He was admitted to another hospital because of three syncopal episodes in one day. He was referred to our hospital because of asymptomatic multiple lacunae indicating cerebral infarction on magnetic resonance imaging. He lost consciousness with convulsion followed by a 70-second interval of cardiac arrest during blood sampling. He reported the onset of his usual prodromal symptoms after 1 min in the 80 degrees head-up tilt position. He lost consciousness 2 min after returning to the supine position. Electrocardiography demonstrated a 10-second interval of cardiac arrest. Magnetic resonance angiography, carotid arterial echography, brain perfusion scintigraphy, and laboratory chemistry and hematology examinations identified no significant findings. Cerebral infarction had occurred in watershed areas, so hemodynamic change during cardiac arrest may be the main cause of the infarctions. He suffered no further syncopal or presyncopal episodes after implantation of a DDD pacing system.

[Successful defibrillation by disconnection of superior vena cava electrode for high defibrillation threshold: a case report].

A 72-year-old man with dilated cardiomyopathy and sustained ventricular tachycardia was treated with amiodarone. He visited another hospital because of loss of consciousness. Electrocardiography showed 2: 1 atrioventricular block. Ambulatory electrocardiography showed total heart beats were 59,700 per day. He was referred to our hospital to evaluate his heart. Several types of ventricular tachycardia and ventricular fibrillation were induced by program stimulation during the electrophysiological study. Therefore, an implantable cardioverter-defibrillator was introduced. During defibrillation threshold tests, ventricular fibrillation could not be terminated by the maximal output of 31J. Despite changing the polarity and lead position, stable defibrillation could not be obtained. Finally, successful defibrillation could only be achieved by disconnection of the superior vena cava electrode.

Long-term follow-up of atrioventricular delay optimization in patients with biventricular pacing.

BACKGROUND: Atrioventricular (AV) delay optimization may be important in patients with biventricular pacing and the optimal AV delay can be predicted using Doppler echocardiography and the formula: optimal AV delay = AV delay-the interval between the end of A wave and complete closure of the mitral valve when the AV delay is set at slightly prolonged AV delay. METHODS AND RESULTS: In the present study the efficacy of this method was evaluated in 5 patients (67.4+/-8.0 (SD) years old) with biventricular pacing. Cardiac output (CO) and diastolic filling time were measured by Doppler echocardiography. When the AV delay was set at the predicted optimal AV delay -25 ms, the predicted optimal AV delay (133+/-66 ms) and predicted optimal AV delay + 25 ms, the respective CO were 4.5+/-0.9, 5.3+/-1.0, 4.8+/-1.0 L/min (p<0.05, ANOVA) and the diastolic filling times were 364 +/-100, 373+/-105, 335+/-84 ms (p<0.05, ANOVA). Congestive heart failure improved from New York Heart Association class 3.6+/-0.5 to 1.4+/-0.5 (p<0.001). CONCLUSIONS: AV delay optimization is important in patients with biventricular pacing and can be easily achieved by the new method.

[Assessment of regional wall motion using strain Doppler imaging during right ventricular bifocal pacing in a patient with severe congestive heart failure: a case report].

A 79-year-old man presented with dilated cardiomyopathy and chronic atrial fibrillation. A DDD pacemaker was implanted due to sick sinus syndrome. His left ventricular ejection fraction was 23%. He was repeatedly admitted with congestive heart failure. Although cardiac resynchronization therapy was attempted, insertion of a pacing lead into the coronary sinus failed. Right ventricular bifocal pacing was done. The QRS width was shortened to 155 msec during bifocal pacing and 157 msec during right ventricular outflow pacing from 221 msec during right ventricular apical pacing. Heart failure was improved from New York Heart Association class III to II. Regional wall motion was assessed by strain of the myocardium. Bifocal pacing increased stroke volume due to improvement of longitudinal dyssynchrony of the septal and lateral walls. Bifocal pacing is effective for patients with severe congestive heart failure in whom biventricular pacing therapy has failed. Strain Doppler imaging is useful for the assessment of regional wall motion during cardiac pacing.