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Biomedical subjects

Jacques Clementy

Publications and source records attributed to Jacques Clementy.

29 records · Page 2Linked to original sources
PubMed2004

Sleep apnea: a new indication for cardiac pacing?

In the general adult population, prevalence of sleep apnea syndrome reaches 4% in men and 2% in women. Continuous positive airway pressure is the most efficient treatment. At the present time, although severe atrial bradycardias could occur during sleep apnea episodes, cardiac pacing has not been demonstrated as an efficient treatment for those bradycardias. Treating sleep apnea generally reduces the number of bradyarrhythmias. However, recent studies reported a beneficial effect of atrial pacing on the sleep apnea burden. The mechanisms rely on two phenomena: first to counteract nocturnal hypervagotonia, and second to treat heart failure. By increasing the heart rate, cardiac output improves, which mitigates pulmonary subedema. Consequently, stimulation of the pulmonary afferent vagal fibers is diminished, which reduces central sleep apnea incidence. During nocturnal hypervagotonia, snoring and obstructive apnea episodes are increased, mainly due to an excessive muscular relaxation of the upper airway area inducing cyclical substantial decreases in the airway caliper. In patients with a low heart rate, atrial pacing can counteract hypervagotonia by enhancing the sympathetic tone and modifying the degree of vigilance. Accordingly, in the near future, sleep apnea treatment might potentially rely on atrial pacing in bradycardic patients with hypervagotonia (with or without heart failure). The role of the physician would then be not only to diagnose sleep apnea, but also to identify potential responders to cardiac pacing.

Adult↗
PubMed2004

Death during polysomnography of a patient with cheyne-stokes respiration, respiratory acidosis, and chronic heart failure.

A patient with chronic heart failure and chronic respiratory failure (CRF) underwent ambulatory polysomnography at home. She was found dead on the morning after the recording. The tracings confirmed severe sleep apnea syndrome. After 8 h of incessant Cheyne-Stokes respiration during sleep, respiratory arrest occurred, followed 7 min later by asystole. This report illustrates a case of respiratory drive failure during sleep as the mode of death in a patient with heart failure, sleep apnea syndrome, and CRF.

Acidosis, Respiratory↗
PubMed2003

Comparison of permanent left ventricular and biventricular pacing in patients with heart failure and chronic atrial fibrillation: a prospective hemodynamic study.

BACKGROUND: Left ventricular pacing (LVP) and biventricular pacing (BVP) have been proposed as treatments for patients with advanced heart failure complicated by discoordinate contraction due to intraventricular conduction delay. For patients in sinus rhythm, BVP works in part by modulating the electronic atrial-ventricular time delay and thus optimizing contractile synchrony, the contribution of atrial systole, and reducing mitral regurgitation. However, little is known of the mechanisms of BVP in heart failure patients with drug-resistant chronic atrial fibrillation. HYPOTHESIS AND METHODS: LVP differs from BVP because hemodynamic and clinical improvement occurs in association with prolongation rather than shortening of the QRS duration. We sought to determine if LVP or BVP improves mechanical synchronization in the presence of atrial fibrillation. Thirteen patients with chronic atrial fibrillation, severe heart failure and QRS >or=140 ms received (after His bundle ablation) a pacemaker providing both LVP and BVP. The mean age was 62 +/- 6 years and left ventricular ejection fraction was 24 +/- 8%. After a baseline phase of one month with right ventricular pacing, all patients underwent in random order 2 phases of 2 months (LVP and BVP). At the end of each phase, an echocardiogram, a hemodynamic analysis at rest and during a 6-minute walking test and a cardio-pulmonary exercise test were performed. RESULTS: LVP and BVP provided similar performances at rest (p = ns). The 6-minute walking test revealed similar performances in both pacing modes but patients were significantly more symptomatic at the end of the test with LVP ( p = 0.035). The cardio-pulmonary exercise test showed higher performances with BVP (92 +/- 34 Watts) vs. LVP (77 +/- 23; p = 0.03). LVP was associated with significantly more premature ventricular complexes recorded during the 6 minute walking test (49 +/- 71) than BVP (10 +/- 23; p = 0.04). CONCLUSIONS: In this small series of patients with atrial fibrillation, congestive heart failure and a prolonged QRS duration, LVP and BVP provided similar hemodynamic effects at rest whereas BVP was associated with better hemodynamic effects during exercise and fewer premature ventricular complexes. Although the mechanisms for the observed differences are uncertain, it is possible that there is worsening of right ventricular function due to a rise in left-to-right electromechanical delay during exercise. Increased catecholamines release might contribute to the lower exercise tolerance and greater number of premature ventricular complexes recorded during exercise observed during LVP compared to BVP. RECOMMENDATIONS: Patients with atrial fibrillation, heart failure and QRS prolongation who are candidates for His-bundle ablation and cardiac resynchronization therapy may respond better to BVP rather than to LVP.

Atrial Fibrillation↗
PubMed2003

Optical mapping technique applied to biventricular pacing: potential mechanisms of ventricular arrhythmias occurrence.

Although it has been suggested that multisite ventricular pacing alleviates heart failure by restoring ventricular electrical synchronization, the respective roles of voltage output, interventricular delay, and pacing sites in the development of ventricular arrhythmias occurrence have not been studied during biventricular pacing or LV pacing. Voltage-sensitive dye was used in eight ischemic Langerdorff-perfused guinea pig hearts to measure ventricular activation times and examine conduction patterns during multisite pacing from three RV and four LV sites. The hearts were stained with di-4-ANEPPS and mapped with a 16 x 16 photodiode array at a resolution of 625 microns per diode. Isochronal maps of RV and LV activation were plotted. Ischemia was produced by gradually halving the perfusion output over 5 minutes. Pacing the RV apex and the base of the LV anterior wall was associated with the most homogeneous and rapid activation pattern (28 +/- 9 vs 41 +/- 12 ms with the other configurations, P < 0.01), and no inducible arrhythmia. In six hearts, ventricular tachycardia could be induced when pacing from the right and left free walls with 20 ms of interventricular delay, at six times the pacing threshold output. In four hearts, simultaneous RV and LV pacing at high voltage output induced ventricular fibrillation with complex three-dimensional propagation patterns, independently of the pacing sites. During biventricular pacing with ischemia, pacing at high voltage output with a long interventricular delay is likely to induce ventricular arrhythmias, particularly when left and right pacing results in a conduction pattern orthogonal to the ventricular myocardial fibers orientation.

Animals↗
PubMed2003

Radiation exposure during radiofrequency catheter ablation for atrial fibrillation.

RF catheter ablation of paroxysmal atrial fibrillation (PAF) is associated with prolonged fluoroscopy. The procedural duration and fluoroscopic exposure to patients and medical staff were recorded and compared among 43 ablation procedures for PAF, 20 for common atrial flutter, and 16 for accessory pathways. Patient radiation exposure was measured by dosimeters placed over the xyphoid, while that of physicians and nurses was measured by dosimeters placed outside and inside the lead apron. The mean fluoroscopy time was 57 +/- 30 minutes for PAF, 20 +/- 10 minutes for common flutter, and 22 +/- 21 minutes for accessory pathway ablation. The patient median radiation exposure was 1110 microSv for PAF, compared with 500 microSv for common flutter and 560 microSv for accessory pathway ablation (P < 0.01). The median radiation exposure to physician and nurse inside the lead apron were, respectively, 2 microSv and 3 microSv for PAF, 1 microSv and 2 microSv for common flutter, and < 0.5 microSv and 3 microSv for accessory pathway ablations. RF catheter ablation for PAF was associated with prolonged fluoroscopy times and a twofold higher radiation exposure to the patient and physician compared with other ablation procedures. Assuming 300 procedures/year, radiation exposure to the medical staff was below the upper recommended annual dose limit.

Atrial Fibrillation↗
PubMed2002

QRST subtraction combined with a pacemap catalogue for the prediction of ectopy source by surface electrocardiogram in patients with paroxysmal atrial fibrillation.

OBJECTIVES: This study evaluated the use of ectopic P-wave morphology to localize pulmonary vein (PV) and non-PV sources of atrial ectopics in patients with paroxysmal atrial fibrillation (PAF). BACKGROUND: The vectorial information embodied in the morphology of ectopic P waves is concealed by overlying T waves. METHODS: The P-wave morphology of 56 ectopics was prospectively analyzed in 44 patients with PAF (age, 52 +/- 12 years; 36 male) by subtracting the adjacent QRST from the QRST-ectopic P-wave complex using custom-designed software. Subtraction fidelity was validated in 15 other patients (55 +/- 19 years, 11 male) by comparing drive beats with simulated ectopics (S2 from the same site) unmasked by subtracting overlying QRST. An algorithm combined with PV pacemaps was used to predict PV sources. Subtracted ectopic P-wave morphologies after PV disconnection were compared with PV and non-PV site pacemaps. Localization was confirmed by mapping and successful ablation. RESULTS: A > or =10-lead electrocardiogram (ECG) match was observed in 92% of 644 simulated ectopics (coupling intervals: 190 to 520 ms). In PAF patients, 37 spontaneous ectopics originated from the PV, while 19 were noted after PV disconnection. Using the P-wave algorithm alone, correct prediction of PV origin was achieved in 30/37 ectopics (81%). Combination with PV pacemaps allowed correct prediction in 34/37 (92%). After PV disconnection, ECG localization predicted successful ablation sites in 16/19 (84%). CONCLUSIONS: Comparison of subtracted ectopic P waves with a pacemap catalogue provides a simple and accurate 12-lead ECG-based method for localization, which can facilitate ablation of arrhythmia triggers irrespective of origin from the PV or elsewhere.

Adult↗
PubMed2002

Left atrial appendage activity masquerading as pulmonary vein potentials.

BACKGROUND: Despite extensive proximal ablation, all potentials frequently cannot be eliminated from the left pulmonary veins (PV). Methods and Results- PV electrograms were analyzed during sinus rhythm, coronary sinus, and left atrial appendage (LAA) pacing, and PV and LAA angiography performed. During pacing, an initial low-amplitude slow potential was recorded on the anterior aspect of the left superior PV and anticipated with shortest activation time by LAA pacing. Its timing coincided with posterior LAA activation, shown to be immediately adjacent to the left superior PV by angiography. In the left inferior PV, the first potential was smaller and less sharp, coinciding with adjacent low LA activation. Angiographically, the LAA was at least 15 mm from the left inferior PV. The second sharper potential in both left PVs was eliminated by proximal ablation. CONCLUSION: Far field LAA activity consistently adds to PV myocardial electrograms in the left superior PV whereas lower, less sharp extravenous potentials in the left inferior PV originate from the inferior LA. They can be identified by LAA and coronary sinus pacing.

Action Potentials↗
PubMed2002

Benefit of atrial pacing in sleep apnea syndrome.

BACKGROUND: Many patients with sleep apnea syndrome have nocturnal bradycardia, paroxysmal tachyarrhythmias, or both, which can be prevented by permanent atrial pacing. We evaluated the effect of using cardiac pacing to increase the heart rate during sleep in patients with sleep apnea syndrome. METHODS: We studied 15 patients (11 men and 4 women; mean [+/-SD] age, 69+/-9 years) with central or obstructive sleep apnea who had received permanent atrial-synchronous ventricular pacemakers for symptomatic sinus bradycardia. All patients underwent three polysomnographic evaluations on consecutive nights, the first night for base-line evaluation and then, in random order, one night in spontaneous rhythm and one in dual-chamber pacing mode with atrial overdrive (basic rate, 15 beats per minute faster than the mean nocturnal sinus rate). The total duration and number of episodes of central or obstructive sleep apnea or hypopnea were analyzed and compared. RESULTS: The mean 24-hour sinus rate during spontaneous rhythm was 57 +/- 5 beats per minute at base line, as compared with 72 +/- 3 beats per minute with atrial overdrive pacing (P<0.001). The total duration of sleep was 321 +/- 49 minutes in spontaneous rhythm, as compared with 331 +/- 46 minutes with atrial overdrive pacing (P=0.48). The hypopnea index (the total number of episodes of hypopnea divided by the number of hours of sleep) was reduced from 9 +/- 4 in spontaneous rhythm to 3 +/-3 with atrial overdrive pacing (P<0.001). For both apnea and hypopnea, the value for the index was 28 +/- 22 in spontaneous rhythm, as compared with 11 +/- 14 with atrial overdrive pacing (P<0.001). CONCLUSIONS: In patients with sleep apnea syndrome, atrial overdrive pacing significantly reduces the number of episodes of central or obstructive sleep apnea without reducing the total sleep time.

Aged↗
PubMed2002

Performance of a rate responsive accelerometer-based pacemaker with autocalibration during standardized exercise and recovery.

The rate responsiveness of a single chamber, accelerometer-based pacemaker with an autocalibration function (Opus G VVIR pacemaker, ELA Medical) was studied with a daily life protocol developed to automatically optimize the programming of accelerometer-based sensors. This new sensor was compared with two other body activity sensors that were manually optimized patient by patient. Forty-three pacemaker recipients (mean age 71 +/- 11 years), paced > 95% of the time, underwent a daily life protocol consisting of rapid walking for 6 minutes (W), climbing upstairs for 1.5 minutes (U), and downstairs for 1.5 minutes (D), alternated by recovery phases. The results were compared with performances measured in a control population of healthy subjects and in two paced patient populations (one equipped with a Dash Intermedics VVIR pacemaker and the other equipped with a Sensolog III Pacesetter/St. Jude VVIR pacemaker). Sex distribution and mean age between paced patients and control subjects were statistically comparable. The mean heartrate achieved by all paced patients at each time sample was compared with the normograms, assigning acceleration (slope) and rate (rate) scores for exercise and recovery phases. Scores ranged from -10 (hypochronotropic) to +10 (hyperchronotropic). Zero represents exact concordance with the responses of healthy individuals, and values between -2.5 and +2.5 were considered statistically similar to normal. During W, although the overall performances of the Dash, Sensolog, and Opus G did not statistically differ from healthy controls, the scores obtained by the Opus G were significantly closer to controls than those of the two other pacemakers (P = 0.02). For U, the three sensors were hypochronotropic (P = 0.03), though the Opus G was associated with a heart rate response closer to that of healthy controls (P = 0.04). D provided similar mean heart rate scores for the Opus G and the Dash compared with healthy controls, in contrast with the hyperchronotropic behavior of the Sensolog (P = 0.02). Opus G revealed a physiological modulation of the heart rate for W and D tests with a slightly hypochronotropic behavior during U. The Opus G autocalibration function provided daily life performances closer to those of healthy controls than two other pacemakers equipped with a body activity sensor that were manually optimized.

Aged↗