[Role of echocardiography in the treatment of heart failure with permanent electric stimulation]. / Ruolo dell'ecocardiografia nel trattamento dello scompenso cardiaco con elettrostimolazione permanente.

Permanent cardiac pacing has been proposed for the treatment of atrioventricular and intraventricular conduction defects and related hemodynamic alterations which may worsen the performance of the failing heart. The initial positive results of right sided atrioventricular synchronous pacing have not been confirmed in later studies involving a larger number of patients with different clinical characteristics. The reason of these conflicting results may be related to the poor understanding of the complex interaction between the adopted pacing mode and the different type, grade and hemodynamic significance of conduction defects. The negative hemodynamic effects of the altered sequence and synchrony of ventricular activation during right sided pacing may outweigh the benefits of an optimal atrioventricular synchrony. Biventricular stimulation has been proposed to improve the electromechanical activation of the left ventricle in patients with left bundle branch block. Ongoing prospective studies are evaluating the potential benefits of biventricular stimulation versus alternative treatments. Although there are no standard indications to cardiac pacing in heart failure it seems that this therapeutic tool may be of value in selected patients with conduction defects which unfavorably affect the cardiac function and that are amenable to be corrected by an appropriate pacing modality. Doppler echocardiography, in its different applications, emerges has a key technique for the selection of patients who may benefit from permanent pacing and for the selection of the best pacing modality. Doppler echocardiography criteria may also be useful in the selection of homogeneous groups of patients to be enrolled in prospective studies aimed at assessing the potential benefits of permanent pacing versus alternative treatments.

Effect of electrode configuration and capacitor size on internal atrial defibrillation threshold using leads currently used for ventricular defibrillation.

BACKGROUND: Previous studies have shown that endocardial atrial defibrillation, using lead configurations specifically designed for ventricular defibrillation, is feasible but the substantial patient discomfort might prevent the widespread use of the technique unless significant improvements in shock tolerability are achieved. It has been suggested that the peak voltage or the peak current but not the total energy delivered determines the patient pain perception and therefore, lower defibrillating voltage and current achieved with modifications in lead and waveforms may increase shock tolerability. This study was undertaken to evaluate the effect, on the atrial defibrillation threshold (ADFT), of the addition of a patch electrode (mimicking the can electrode) to the right ventricle (RV)-superior vena cava (SVC) lead configuration. The influence of capacitor size on ADFT using the RV-SVC+skin patch configuration was also assessed. METHODS: In 10 patients (pts) (Group 1) cardioversion thresholds were evaluated using biphasic shocks in two different configurations: 1) right ventricle (RV) to superior vena cava (SVC); 2) RV to SVC+skin patch. In a second group of twelve patients (Group 2) atrial defibrillation thresholds of biphasic waveforms that differed with the total capacitance (90 or 170 microF) were assessed using the RV to SVC+skin patch configuration. RESULTS: In Group 1 AF was terminated in 10/10 pts (100 %) with both configurations. There was no significant difference in delivered energy at the defibrillation threshold between the two configurations (7.1 +/- 5.1 J vs 7.1 +/- 2.6 J; p < 0.05). In group 2 AF was terminated in 12/12 pts (100%) with both waveforms. The 170 microF waveform provided a significantly lower defibrillating voltage (323.7 +/- 74.6 V vs 380 +/- 70.2 V; p < 0.03) and current (8.1 +/- 2.7 A vs 10.0 +/- 2.3 A; p < 0.04) than the 90 microF waveform. All pts, in both groups, perceived the shock of the lowest energy tested (180 V) as painful or uncomfortable. CONCLUSIONS: The addition of a patch electrode to the RV-SVC lead configuration does not reduce the ADFT. Shocks from larger capacitors defibrillate with lower voltage and current but pts still perceive low energy subthreshold shocks as painful or uncomfortable.

[The concurrent implantation of a last-generation automatic defibrillator and a 2-chamber pacemaker]. / Impianto concomitante di defibrillatore automatico di ultima generazione e pacemaker bicamerale.

BACKGROUND: Potentially lethal interactions between concomitantly implanted pacemaker and automatic first-generation cardioverter-defibrillator have been reported. We therefore evaluated the reliability and safety of simultaneous implantation of dual-chamber pacemakers with a fourth generation cardioverter-defibrillator incorporating an improved arrhythmia detection system. METHODS: Concomitant implantation of an automatic cardioverter defibrillator and a dual-chamber pacemaker was performed in four patients for malignant tachyarrhythmias and symptomatic bradycardia. Two Jewel 7219C and two Micro Jewel 7223 (Medtronic Inc.) implantable cardioverter defibrillators were connected to an endocardial lead (Medtronic Mod. 6936). In 2 patients with a previously implanted cardioverter-defibrillator, the pacemaker was connected to bipolar atrial and ventricular leads. In the 2 patients who already had a dual-chamber pacemaker, the unipolar pacing leads implanted previously were used. At the time of implantation of the second device, interaction testing was performed evaluating ventricular fibrillation detection during high-output asynchronous pacing. Testing for malfunctions, reprogramming or variations of pacing thresholds of the pacemakers after electric shocks was also carried out. Moreover, intracavitary signals, stimulation thresholds and electrical therapies delivered were evaluated during follow-up. RESULTS: During interaction testing, induced ventricular fibrillation was detected, with no delay, in 4/4 cases (100%). After a mean follow-up of 6.3 +/- 5 months (range 2-13), 5 shocks for ventricular fibrillation, 10 shocks for fast ventricular tachycardia and 72 antitachycardia pacings were delivered. All these electrical therapies were considered appropriate. No symptomatic sustained tachyarrhythmia remained undetected. CONCLUSIONS: These data suggest that concomitant implantation of a fourth-generation automatic cardioverter-defibrillator and a dual-chamber pacemaker using either unipolar or bipolar leads can be performed safely. Extreme caution and rigorous interactions testing is nevertheless advised when considering this device combination.

[Improvement of postinfarct left myocardial contractile function after administration of diltiazem]. / Ripresa contrattile di asinergie miocardiche postinfartuali indotta dalla somministrazione acuta di diltiazem.

BACKGROUND: The impairment of intracellular calcium homeostasis is an important biochemical alteration in stunned and hibernating myocardium. These different forms of viable myocardium frequently occur after myocardial infarction and their recognition may modify the therapeutic program and prognosis. Experimental studies and experiences on male subjects have demonstrated that calcium-channel blockers exert a protective action on myocardial reperfusion injury and reduce infarct size. OBJECTIVES: The aim of the present study was to evaluate the efficacy of i.v. diltiazem (i.e. a calcium-channel blocker with negative inotropic effect) in enhancing the contractility of viable akinetic myocardium in patients after myocardial infarction. METHODS: Sixty patients (52 males and 8 females, age 57 +/- 10 years) with the first acute myocardial infarction were evaluated with dobutamine-echocardiography 9 +/- 2 days after admission and on the following day with diltiazem-echocardiography. Diltiazem was administered i.v. using repeated boluses of 0.25 mg/kg up to the maximum dose of 1 mg/kg. Before and during the infusion, left ventricular regional function was scored and the Wall Motion Score Index (WMSI) was calculated; ECG and arterial blood pressure were also monitored. Results were compared with low-dose dobutamine-echocardiography. In a subset of 13 patients who underwent myocardial revascularization (7 coronary artery by-pass graftings and 6 percutaneous transluminal angioplasties), post-procedure echocardiograms were performed to evaluate whether regional left ventricular function had improved. RESULTS: Low-dose dobutamine and diltiazem enhanced regional left ventricular contractility in 28 and 31 patients, respectively; both tests were positive in 26 cases. Conversely, dobutamine-test was negative in 32 patients and diltiazem in 29, with concordance in 27. A good correlation was found between diltiazem and dobutamine WMSI at the basal evaluation (r = 0.91; p < 0.000) as well as during the pharmacological test (r = 0.86; p < 0.000). In patients who underwent myocardial revascularization, the same good correlation was found between diltiazem-WMSI and WMSI evaluated after the procedure (r = 0.91; p < 0.000). CONCLUSIONS: Acute i.v. administration of diltiazem about ten days after myocardial infarction may enhance the contractility of viable akinetic ventricular wall segments, as evaluated with echocardiography. The results of this study may have some physiopathological and therapeutical implications that could lead to reconsidering the use of calcium-channel blockers, particularly diltiazem, in selected patients after myocardial infarction.

[Atrial thrombosis following the low-energy DC internal countershock of chronic AF: considerations of a clinical case]. / Trombosi auricolare post dc-shock interno a bassa energia della FA cronica: considerazioni su un caso clinico.

Embolism may occur after cardioversion of atrial arrhythmias, especially atrial fibrillation, despite the apparent exclusion of preexisting atrial thrombus. This is related to the now well-known phenomenon of "atrial stunning" following either electrical or pharmacological cardioversion. It has also been suggested that "de novo" atrial thrombus formation after cardioversion could be responsible for the embolic event. We report a case of low-energy internal cardioversion of chronic atrial fibrillation in a patient with recurrent episodes of heart failure followed by a de novo left appendage thrombus formation. The patient, followed clinically and by repeated transesophageal echocardiograms, did not show any clinical sign of thromboembolism and the left appendage thrombus regressed completely, as demonstrated on the transesophageal echocardiogram.

Internal cardioversion of chronic atrial fibrillation in patients.

Transvenous internal cardioversion of chronic AF using a right atrium (RA) coronary sinus (CS) vector requires more energy than cardioversion of paroxysmal AF. Chronic AF is not terminated in 25% of patients using biphasic shocks up to 10 J. We therefore evaluated efficacy, safety, and tolerability of internal cardioversion using a "unipolar" configuration (RA to skin patch) and biphasic shocks in patients with long-lasting AF and different heart disease. In each patient, biphasic R wave synchronous shocks were delivered between a large defibrillating surface area electrode in the RA and a skin patch in the left prepectoral position. Defibrillation protocol started with a test shock of 0.4 J. Shocks were repeated and increased until termination of AF or a maximum of 34 J. Sedation was used when the patient described the shock as painful. This study included 11 patients with a mean age of 67 +/- 8 years (range 56-83). AF duration was > or = 1 month in all patients with a mean duration of 11 +/- 11 months (range 2-36). Underlying heart disease was present in all patients and the mean left atrial dimension was 43 +/- 9 mm (range 26-57). AF was terminated in 10 of 11 patients (91%) with a mean delivered energy of the successful shocks of 18.7 +/- 8.7 J (median energy 16.9 J; range 7.3-32.5) and a mean leading edge voltage of 564 +/- 129 V. The mean shock impedance at the defibrillation threshold was 71 +/- 13 omega (range 59-103). A total of 131 shocks were delivered without any complication and proarrhythmia episodes. We conclude that low energy "unipolar" internal cardioversion is a simple, safe, and effective technique for termination of chronic AF in patients with heart disease. The procedure is often tolerated under light sedation.