Biomedical subjects

N Louvros

Publications and source records attributed to N Louvros.

12 recordsLinked to original sources

PubMed2000

Modulation of the sympathovagal balance in drug refractory dilated cardiomyopathy, treated with permanent atrioventricular sequential pacing.

The aim of this study was to assess the long term efficacy of DDD pacing mode in selected patients with idiopathic dilated cardiomyopathy (IDCM) and drug refractory heart failure. The patients were evaluated according to the long term alteration of the sympathovagal balance (SVB). Patients with IDCM were considered eligible for DDD pacing if during temporary VDD pacing a 15% or more increase in the resting cardiac output was demonstrated. From the 29 patients studied, finally 20 patients (15M, 5F, 69 +/- 10 years) fulfilled the aforementioned criterion and therefore were considered candidates for permanent DDD pacing (NYHA class: 3.5 +/- 0.3, Ejection fraction: 27 +/- 7%, Resting cardiac index (CI) 2.6 +/- 0.4 l/min). The ECG of the patients demonstrated LBBB in 13, RBBB in 4 and RBBB + LAH in 3, with a PR interval of 232 +/- 28 ms and QRS duration of 138 +/- 15 ms. The pacemaker was programmed at 40-150 bpm, and AV delay of 105 +/- 20 ms. The lower heart rate programmed, in conjunction with the heart failure state of these patients, was responsible for essentially continuous atrial tracking, ventricular pacing. We evaluated the SVB in the pre- and post-implant periods (3rd and 6th month), using the hourly power spectral analysis (PSA) of heart rate variability during 24 hour Holter monitoring. As SVB we considered the ratio: low (0.04-0.15 Hz) to high frequency (0.15-0.40 Hz). We compared the SVB (LF/HF) during the day and night time for the pre- and post-implant periods. Post-pacing, the NYHA class was significantly improved (2.9 +/- 0.2 and 2.7 +/- 0.3 the 3rd and 6th month respectively). The mean heart rate was 78 +/- 8 bpm in the 3rd and 80 +/- 7 bpm in the 6th month postoperatively, which was lower than the 84 +/- 9 bpm preoperatively, but this difference did not reach statistical significance. During the night time the LF/HF decreased from 1.45 +/- 0.2 (LF: 7.19 +/- 0.43, HF: 4.95 +/- 0.54) in the pre-implant period to 0.9 +/- 0.09 (p < 0.001) (LF: 6.96 +/- 0.63, HF: 7.73 +/- 0.48) in the 3rd month. No further changes were observed in the 6th month (0.82 +/- 0.05, p = NS) (LF: 6.83 +/- 0.51, HF: 8.53 +/- 0.86) compared to the 3rd month. During the day time the LF/HF decreased from 1.5 +/- 0.5 (LF: 7.87 +/- 0.67, HF: 5.24 +/- 0.32) to 1.43 +/- 0.6 (p = NS) (LF: 7.34 +/- 0.71, HF: 5.24 +/- 0.42) in the 3rd month and to 1.41 +/- 0.09 in the 6th month (p = NS) (LF: 7.51 +/- 0.74, HF: 5.36 +/- 0.63). Comparing the LF/HF of day and the night time period, while in the pre-implant period there was no significant difference (1.5 +/- 0.5 vs 1.45 +/- 0.2, p = NS), the difference became significant in the 3rd (1.43 +/- 0.6 vs 0.9 +/- 0.09, p < 0.001) and 6th month (1.41 +/- 0.09 vs 0.82 +/- 0.05, p < 0.001). In conclusion, DDD pacing with individualized AV delay as an adjunct therapy could be a valuable method in selected patients with IDCM and drug refractory heart failure. DDD pacing improves the SVB over the long term. This improvement is attributed to sympathetic activity withdrawal and is more pronounced during night and less during day time.

Aged↗

PubMed1998

Atrial septal pacing to synchronize atrial depolarization in patients with delayed interatrial conduction.

The current method of pacing the right atrium from the appendage or free wall is often the source of delayed intraatrial conduction and discoordinate left and right atrial mechanical function. Simultaneous activation of both atria with pacing techniques involving multisite and multilead systems is associated with suppression of supraventricular tachyarrhythmias and improved hemodynamics. In the present study we tested the hypothesis that pacing from a single site of the atrial septum can synchronize atrial depolarization. Five males and two females (mean age 58 +/- 6 years) with drug refractory paroxysmal atrial fibrillation (AF) were studied who were candidates for AV junctional ablation. All patients had broad P waves (118 +/- 10 ms) on the surface ECG. Multipolar catheters were inserted and the electrograms from the high right atrium (HRA) and proximal, middle, and distal coronary sinus (CS) were recorded. The atrial septum was paced from multiple sites. The site of atrial septum where the timing between HRA and distal CS (d-CS) was < or = 10 ms was considered the most suitable for simultaneous atrial activation. An active fixation atrial lead was positioned at this site and a standard lead was placed in the ventricle. The interatrial conduction time during sinus rhythm and AAT pacing and the conduction time from the pacing site to the HRA and d-Cs during septal pacing were measured. Atrial septal pacing was successful in all patients at sites superior to the CS o.s. near the fossa ovalis. During septal pacing the P waves were inverted in the inferior leads with shortened duration from 118 +/- 10 ms to 93 +/- 7 ms (P < 0.001), and the conduction time from the pacing site to the HRA and d-CS was 54.3 +/- 6.8 ms and 52.8 +/- 2.5 ms, respectively. The interatrial conduction time during AAT pacing was shortened in comparison to sinus rhythm (115 +/- 18.9 ms vs 97.8 +/- 10.3 ms, P < 0.05). In conclusion, simultaneous activation of both atria in patients with prolonged interatrial conduction time can be accomplished by pacing a single site in the atrial septum using a standard active fixation lead placed under electrophysiological study guidance. Such a pacing system allows proper left AV timing and may prove efficacious in preventing various supraventricular tachyarrhythmias.

Atrial Fibrillation↗

PubMed1997

Circadian modulation of ventricular tachycardia cycle length variability in ICD patients with dilated cardiomyopathy.

VT is usually characterized by stability of the RR intervals after a few cycles from the onset. The aim of this study was to evaluate the VT cycle length (VTCL) variability in patients with dilated cardiomyopathy (DCM), in whom a third-generation ICD was previously implanted. Eighty-three episodes of VT were analyzed in 10 patients (8 male, 2 female, 65 +/- 6 years) with DCM, and NYHA Class II (7 patients) or III (3 patients). As an index of VTCL variability, the coefficient of variance of the last 15 consecutive RR intervals (CVRR) of the detected and stored VT by the device was considered. The mean value of the RR intervals and the mean value of CVRR of the VT episodes recorded during day versus night time were compared. Fifty-five VT episodes were recorded during the day and 28 episodes during the night time. The mean RR intervals of VT episodes during day time was 335 +/- 29 ms and during the night time was 350 +/- 22 ms (P = NS). The mean CVRR of VT episodes during day time and night time were 2.83 +/- 0.52 and 3.36 +/- 0.48, respectively (P = 0.017). In conclusion, a circadian modulation of VTCL variability exists in patients with DCM. The VTCL variability is less during day time compared to night time. A possible explanation is a circadian alteration of sympathovagal balance modifying the electrophysiological properties of the arrhythmogenic substrate.

Aged↗

PubMed1996

Congestive heart failure and VVI pacing mode: dynamic behavior of the dispersion of ventricular repolarization.

Dynamic Behavior of the Dispersion of Ventricular Repolarization. The aim of this study was to evaluate the circadian variation in the spatial dispersion of ventricular repolarization in continuously paced patients with congestive heart failure (CHF). Fourteen patients (10 males, 4 females, aged 65 +/- 8 years) with CHF due to dilated cardiomyopathy (DCM) and an echocardiographic ejection fraction of 28% +/- 3% were studied. All patients underwent AV junctional RF ablation and permanent pacemaker implantation for drug refractory chronic atrial fibrillation (AF). Patients were evaluated at 1 month postimplant with a three-channel 24-hour Holter monitor, using the three plane Frank orthogonal leads (X, Y, and Z), in VVI pacing mode at 70 beats/min. For each hour, the mean value of spike-T interval dispersion of the first five beats was measured. The control group consisted of 20 patients without structural heart disease, but with AF and complete AV block, continuously paced in VVI mode at 70 beats/min. The dispersion of the spike-T interval had a circadian behavior in the study population, with higher values at night and lower during the daytime. During the daytime, the mean value of spike-T interval dispersion was 39 +/- 5 ms and during the nighttime it was 45 +/- 7 ms (P = 0.003). Such a difference between day and night was not found in the control group (38 +/- 6 ms and 40 +/- 8 ms, respectively, P = NS). In the daytime period the mean value of spike-T interval dispersion of our study population was comparable to that of the control group (P = NS), while during the nighttime it was significantly higher (P = 0.0004). In conclusion, by evaluating the dispersion of ventricular repolarization in two dimensions, space and time, a circadian variation was found in paced patients with CHF due to DCM. The increased QT dispersion in these patients during the nighttime period was attributed to different effects of vagal activity in normal and abnormal myocardial areas.

Aged↗

PubMed1971