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Biomedical subjects

Antonio Michelucci

Publications and source records attributed to Antonio Michelucci.

13 recordsLinked to original sources
PubMed2004

A perspective on atrioventricular delay optimization in patients with a dual chamber pacemaker.

Atrioventricular delay (AVD) is critical in patients with DDD pacemakers (PM). Echo/Doppler evaluation of AVD providing the longest left ventricular filling time (FT) or the highest cardiac output (CO) is used for AVD optimization. Recently myocardial performance index (MPI) has been shown to improve by optimizing AVD. The aim was to compare the CO, FT, MPI derived optimal AVD, and to analyze systolic and diastolic performance at every optimal AVD. Twenty-five patients, 16 men 68 +/- 11 years, ejection fraction >or= 50%, with a DDD PM for third-degree AV block, without other major cardiomyopathies, underwent echo/Doppler AVD optimization. CO, FT, and MPI derived optimal AVDs were identified as the AVDs providing the highest CO, the longest FT, and the minimum MPI, respectively. Isovolumic contraction and relaxation time (ICT, IRT), ejection time (ET), ICT/ET, and IRT/ET ratios were also evaluated at every optimal AVD. CO, FT, and MPI derived optimal AVDs were significantly different (148 +/- 36 ms, 116 +/- 34 ms, and 127 +/- 33 ms, respectively). ICT/ET was similar at CO, FT, and MPI derived optimal AVD (0.22 +/- 0.10, 0.23 +/- 0.11, and 0.21 +/- 0.10, respectively). IRT/ET ratio was similar at FT and MPI derived optimal AVDs (0.34 +/- 0.15 and 0.33 +/- 0.15, respectively) and significantly shorter (P < 0.02) than at CO derived optimal AVD (0.40 +/- 0.15). Different methods indicate different optimal AVDs. However analysis of systolic and diastolic performance shows that different AVDs result in similar systolic or diastolic performance. At MPI optimized AVD, a high CO combined with the most advantageous conditions of both isovolumic contraction and relaxation phases is achieved.

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PubMed2004

Atrial septal pacing: a new approach to prevent atrial fibrillation.

Atrial pacing may prevent the onset of atrial fibrillation (AF) because of: (1) prevention of the relative bradycardia that triggers paroxysmal AF; (2) prevention of the bradycardia induced dispersion of refractoriness; (3)suppression or reduction of premature atrial contractions that initiate reentry and predispose to AF; (4) preservation of AV synchrony, which might prevent switch induced changes in atrial repolarization predisposing to AF. Atrial pacing locations that decrease atrial activation and dispersion of refractoriness may be preferable in patients with a history of AF. Two different interatrial septum sites have been proposed: the Bachmann's bundle and the coronary sinus ostium. The results of two prospective randomized studies indicate that septal pacing, when compared to the traditional right atrial appendage pacing, significantly reduces : (1) paroxysmal AF recurrences and burden; and (2) progression to chronic AF.

Animals↗
PubMed2004

Myocardial perfusion imaging using gated SPECT in heart failure patients undergoing cardiac resynchronization therapy.

UNLABELLED: Cardiac resynchronization therapy (CRT) by biventricular pacing is indicated in patients with severe heart failure and left bundle branch block who remain symptomatic despite optimal medical therapy. The relationship between baseline resting perfusion pattern and hemodynamic response to CRT has not been fully investigated. We tested the usefulness of perfusion gated SPECT for baseline evaluation and follow-up of these patients. METHODS: In 20 patients, we performed gated SPECT before CRT and at the 3-mo follow up. Left ventricular (LV) ejection fraction (EF), end-diastolic (ED) and end-systolic (ES) volume indexes (VI), and wall motion score index (WMSI) were measured and compared with clinical outcome. RESULTS: One patient died before follow-up. The 19 remaining patients were classified into 1 of 2 groups according to the presence (group A) or absence (group B) of a significant severe perfusion defect at baseline before CRT. At the 3-mo follow-up, 6 of 10 group A and 8 of 9 group B patients had an improvement in New York Heart Association class. In both groups, quality of life, 6-min walking distance, and WMSI significantly improved. In group A, no significant change was registered in LVEF, LVEDVI, or LVESVI. In group B, LVEF increased from 23.1% +/- 8% to 27.1% +/- 11% (P < 0.03) and LVEDVI and LVESVI decreased from 159 +/- 70 mL to 135 +/- 68 mL (P < 0.02) and from 127 +/- 67 mL to 104 +/- 65 mL (P < 0.01), respectively. CONCLUSION: Perfusion gated SPECT appears useful to characterize and follow up candidates for CRT. Despite clinical improvement, patients with severe resting perfusion defects do not show significant improvement in LVEF or reduction in LV volumes.

Aged↗
PubMed2003

A new algorithm for closed-loop stimulation: a feasibility study.

Closed-loop stimulation (CLS) is a physiological system for adaptive rate pacing based on monitoring and processing of the intracardiac impedance. The "standard" CLS algorithm (SCLS) requires continuous ventricular pacing. A new, enhanced CLS algorithm (ECLS) provides rate modulation during sensed and paced ventricular depolarizations. The aim of this study was to validate ECLS and to compare its effectiveness with that of SCLS. Ten patients received Inos2+ CLS pulse generators. SCLS and ECLS were uploaded to the device and evaluated in a randomized, crossover fashion at 30 and 45 days after pacemaker implantation. At each follow-up visit, ambulatory and posture tests were performed. Heart rate (HR) during daily activity was evaluated based on 24-hour Holter recordings. During all phases of the ambulatory test, both algorithms provided physiologically appropriate rates in all patients. The proportion of sensed ventricular events was significantly higher in ECLS (93.9%) than in SCLS (0.7%). The proportion of paced ventricular events during 24 hours was substantially lower with ECLS (25.7%) than with SCLS (98.4%). Postural changes did not influence HR with either algorithm. The Holter recordings indicated prompt, safe, and effective rate modulation appropriate to patients activity. In conclusion, analysis of these clinical data demonstrated the safety and effectiveness of the ECLS algorithm. Moreover, with this algorithm the ventricle is paced only when required, which may be expected to retard battery depletion and retain the natural ventricular activation pattern whenever possible.

Aged↗
PubMed2003

Angiotensin-converting enzyme and endothelial nitric oxide synthase polymorphisms in patients with atrial fibrillation.

Experimental studies have shown a significant increase in angiotensin-converting enzyme (ACE) expression in atrial tissue of AF patients. ACE regulates the synthesis of endothelial nitric oxide (NO), which modulates autonomic nervous activity involved in the development of AF. The aim of the study was to evaluate the prevalence of ACE insertion/deletion and endothelial NO synthase (eNOS) T-786C, G894T, and 4a/4b polymorphisms in 148 patients with persistent AF, compared with 210 control subjects. ACE insertion/deletion polymorphism genotype distribution and allele frequency were significantly different between patients and controls (P < 0.0001 and P < 0.0001, respectively). ACE DD genotype was significantly associated with the risk of AF (OR DD/ID + II = 3.24, P < 0.0001). Analysis of eNOS polymorphisms showed no significant difference in genotype distribution and allele frequency between patients and controls. The results suggest a possible role of ACE DD genotype as a predisposing factor to AF and a pathophysiological mechanism of ACE inhibition in reducing the incidence of AF in patients with left ventricular dysfunction.

Aged↗
PubMed2003

Atrial activation analysis by surface P wave and multipolar esophageal recording after cardioversion of persistent atrial fibrillation.

We studied atrial activation during sinus rhythm by combining 12-lead ECG and multipolar esophageal recordings in 30 patients after electrical cardioversion of persistent atrial fibrillation. The primary endpoint was to establish a correlation between atrial activation evaluated by the two methods. Total P wave duration and morphology in inferior leads identified three patterns: normal P wave, late-positive P wave, and late-negative P wave. Proximal and distal esophageal recording characterized the longitudinal direction of activation of the posterior left atrium. We distinguished three activation patterns: normal activation when the interatrial conduction time is normal and depolarizes in craniocaudal direction, delayed activation when the interatrial conduction time is prolonged and the craniocaudal activation is maintained, and finally reversed activation when the posterior left atrium depolarizes in a reversed caudocranial direction. Four patients showed a normal P wave and also had a normal esophageal activation. Twelve patients showed a prolonged P wave (associated with delayed esophageal activation in 10 patients and reversed activation in 2 patients); 14 patients had a late-negative P wave (all associated with a reversed esophageal activation). A high correlation existed between each pattern obtained by surface ECG and esophageal recording (P < 0.001) and between surface P wave duration and interatrial conduction time (R2 = 0.64, P < 0.001). Much information concerning atrial activation can be obtained by meticulous analysis of the P wave, particularly its terminal part. Multipolar esophageal recording can be used when surface ECG appears unclear.

Aged↗
PubMed2003

Prevention of paroxysmal atrial fibrillation in patients with sinus bradycardia: role of right atrial linear ablation and pacing site.

INTRODUCTION: Right atrial linear lesions (RALL), either alone or in combination with antiarrhythmic drug therapy, may modify the substrate for maintenance of atrial fibrillation (AF). The aim of this prospective randomized study was to determine whether RALL provides additional benefit to right atrial appendage pacing (RAAP) and/or interatrial septum pacing (IASP) and drug therapy in patients with symptomatic paroxysmal AF and sinus bradycardia requiring permanent atrial pacing. METHODS AND RESULTS: Sixty-four patients (33 men and 31 women, mean age 73 +/- 10 years) completed the 6-month follow-up. Patients were randomized to either RALL (n = 33) or non-right atrial linear lesions (NRALL), and then to either IASP (n = 32) or RAAP (n = 32). Fifteen RALL patients were paced at the IAS and 18 at the RAA. Seventeen NRALL patients were paced at the IAS and 14 at the RAA. No statistical difference was observed with regard to the mean atrial tachyarrhythmia (AT) burden between NRALL (84 +/- 169 min/day) and RALL patients (202 +/- 219 min/day). Mean AT burden was significantly lower in the IASP group (70 +/- 150 min/day) than in RAAP group (219 +/- 317 min/day; P < 0.016). In the RALL group, the mean AT burden was 99 +/- 180 min/day in the IASP patients and 288 +/- 372 min/day in the RAAP patients (P < 0.046). In the NRALL group, no statistical difference in the mean AT burden was observed between IASP patients (46 +/- 117 min/day) and RAAP patients (130 +/- 211 min/day). CONCLUSION: The results of the present study indicate that RALL did not provide any additional therapeutic benefit to combined antiarrhythmic drug therapy and septal or nonseptal atrial pacing in patients with sinus bradycardia and paroxysmal AF.

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PubMed2003

[Normal and abnormal atrial activation. An update with special reference to surface electrocardiogram].

Surface electrocardiogram is commonly used to evaluate the normal and abnormal activation of the atria. Interatrial conduction appears as the most important factor determining P wave duration and morphology during sinus rhythm. A good estimation of the interatrial conduction time can be obtained by a simple esophageal recording or by P wave duration on the surface electrocardiogram. A careful analysis of the ectopic atrial beats on the 12-lead electrocardiogram can identify the site of origin of the ectopic atrial beat. Surface electrocardiogram is commonly used in the classification of atrial flutter.

Atrial Flutter↗
PubMed2002

P wave assessment: state of the art update.

Diagnostic (mapping) and therapeutic (ablation, pacing) advances have provided insight into atrial depolarization processes and new developments in P wave analysis. Information about interatrial pathways is important to the understanding of interatrial conduction delay. A standardized method for P wave analysis is necessary for the development of a clinical role for management of patients with paroxysmal atrial fibrillation using signal-averaged P wave analysis and P wave dispersion. Algorithms for predicting localization of ectopic P waves may facilitate catheter ablation. P wave changes due to pacing at different atrial sites may be useful for permanent pacing for prevention of atrial fibrillation. Introduction of these developments into clinical practice should allow better prevention and treatment of atrial arrhythmias and could have considerable impact in view of their high frequency especially in the older population.

Algorithms↗
PubMed2002

How to test mode switching in pacemakers implanted in patients: the MOST study.

Optimal management of atrial arrhythmias with dual chamber pacemakers requires proper performance of automatic mode switching (AMS). The aim of this study was to develop a reliable technique to test the AMS function by using an external electronic device capable of mimicking the occurrence of supraventricular arrhythmias (Supraventricular Arrhythmia Simulator [SAS]). The SAS delivers low voltage pulse trains (200 mV, 20 ms) through two skin electrodes. Each pulse train lasts 15 seconds and starts synchronously with a pacing pulse of the implanted pacemaker to avoid interference from the operator. The pulse train rate is set at 350, 250, and 160 beats/min to simulate AF, atrial flutter, and atrial tachycardia (AT), respectively. Thirty-five patients implanted with Vitatron pacemakers, whose AMS system has been previously validated, were enrolled. Atrial and ventricular sensing were programmed in unipolar mode at 0.5 mV and in bipolar mode at > 2 mV, respectively. All pulses from the SAS were detected by the atrial channel at an amplitude ranging from 1 to 3 mV. The test proved to be safe and reliable at rest and during exercise. AMS occurred immediately at onset or at offset of atrial arrhythmias, and no adverse interference on pacemaker function was seen from the SAS. In conclusion, the described technique and the SAS are safe and reliable for patient and pacemaker function and can be proposed as a useful method to verify proper performance of AMS function irrespective of the type of implanted devices.

Aged↗
PubMed2002

Interatrial septum pacing avoids the adverse effect of interatrial delay in biventricular pacing: an echo-Doppler evaluation.

AIMS: Biventricular pacing (BVP) can improve haemodynamics in patients with dilated cardiomyopathy (DCM) and left bundle branch block by reducing interventricular delay (IVD). Since in DCM interatrial delay (IAD) and IVD frequently coexist, the aim of this study was to test the hypothesis that IVD reduction associated with IAD produces an imbalance between the programmed right atrioventricular (AV) delay and the effective AV delay on the left, and that interatrial septum pacing (IASP) combined with BVP overcomes this adverse effect. METHODS AND RESULTS: IAD, IVD, left and right mechanical atrioventricular delay (L-RMAVD) were measured by echo-Doppler in 29 patients with BVP: 17 patients (Group A) had the atrial lead in the right atrial appendage, 12 patients (Group B) who experienced paroxysmal atrial fibrillation had the atrial lead on the interatrial septum. In Group A, LMAVD was significantly shorter than RMAVD (172 +/- 24 vs 207 +/- 24 ms, P<0.002), IAD was significantly longer than IVD (52 +/- 24 vs 21 +/- 18 ms, P<0.0001). In Group B, no differences were observed between LMAVD and RMAVD (187 +/- 32 vs 185 +/- 28 ms, NS), and between IAD and IVD (11 +/- 12 vs 13 +/- 16 ms, NS). CONCLUSIONS: IAD produces different left and right atrioventricular sequences in BVP. IASP combined with BVP, by resynchronizing both atria and ventricles, is able to avoid this adverse effect.

Aged↗
PubMed2002

Simultaneous assessment of electrocardiographic parameters for risk stratification: validation in healthy subjects.

BACKGROUND: Sudden cardiac death represents a major public health problem, but in the general population the identification of those subjects at very high risk remains poor. Simultaneous multiparametric ECG analysis can improve the identification of high-risk patients. METHODS: Five-min ECG recordings at a 5 MHz sampling rate (extended length-XL-ECG, Mortara Instruments, Milwaukee, WI, USA) were acquired in 105 healthy subjects (age range 21 to 80 years), equally distributed for age decades and sex, and three additional recordings, 30 min apart, were repeated in 30 subjects on the second day. The following parameters were recorded and analyzed: the RR interval, QRS duration, QT interval corrected according to the Bazett and Fridericia formulae, QT dispersion, T wave complexity, activation-recovery interval dispersion, standard deviation of the RR intervals, filtered QRS duration, the square root of the mean voltage of the last 40 ms of the filtered QRS, and the length of time that the terminal vector magnitude complex remains < 40 microV. RESULTS: QRS duration, activation-recovery interval dispersion, and filtered QRS differed in the two sexes. The standard deviation of the RR intervals, T wave complexity and QT dispersion were significantly correlated with age. The reproducibility was good for each parameter. CONCLUSIONS: The XL-ECG allows the simultaneous calculation of eight adequately reproducible different parameters the values of which are in agreement with those of the literature. Thus, XL-ECG is a reliable time- and cost-saving tool.

Adult↗