Jacques Mugica

Four chamber pacing in dilated cardiomyopathy

A 54‐year‐old man received a four chamber pacing system for severe congestive heart failure (NYHA functional Class IV). His ECG showed a left bundle branch block (200‐msec QHS duration) with 200‐msec PR interval, normal QRS axis, and 90‐msec interatrial interval. An acute hemodynamic study with insertion of four temporary leads was performed prior to the implant, which demonstrated a significant increase in cardiac output and decrease of pulmonary capillary wedge pressure. A permanent pacemaker was implanted based on the encouraging results of the acute study. The right chamber leads were introduced by cephalic and suhcla vian approaches. The left atrium was paced with a coronary sinus lead, Medtronic SP 2188–58 model. An epicardial Medtronic 5071 lead was placed on the LV free wall. The four leads were connected to a standard bipolar DDD pacemaker. Chorus 6234. The two atrial leads were connected via a Y‐connector to the atrial channel of the pacemaker with a bipolar pacing configuration. The two ventricular leads were connected in a similar fashion to the ventricular channel of the device. The right chamber leads were connected to the distal poles. The left chamber leads were connected to the proximal poles of the pacemaker. Six weeks later, the patients clinical status improved markedly with a weight loss of 17 kg and disappearance of peripheral edema. His functional class was reduced to NYHA II. Four chamber pacing is technically feasible. In patients with evidence of interventricular dyssynchrony, this original pacing mode probably provides a mechanical activation sequence closer to the natural one. We doubt that this technique will have an impact on long‐term survival, but it could be of major importance to improve the patients well‐being and control heart failure.

Multisite pacing for end-stage heart failure : early experience

Our objective was to improve hemodynamics by synchronous right and left site ventricular pacing in patients with severe congestive heart failure (CHF). Previous studies reported a benefit of dual chamber pacing with a short AV delay in patients with severe CHF. Other works, however, show contradictory results. Deleterious effects due to a desynchronization of right (RV) and left ventricular (LV) contractions have been suggested. This study included eight subjects with widened QRS and end‐stage heart failure despite maximal medical therapy, who refused, or were not eligible to undergo heart transplantation. Each patient underwent a baseline, invasive hemodynamic evaluation with insertion of three temporary leads to allow different pacing configurations, including RV apex and outflow tract pacing, and biventricular pacing between the RV outflow tract and LV and RV apex and LV. According to the results of this baseline study, the configuration of preexistent pacemakers was modified or new systems were implanted to allow biventricular pacing, which, in patients with sinus rhythm, was atrial triggered. Biventricular pacing increased the mean cardiac index (CI) by 25% (from a baseline of 1.83 ± 0.30 L/min per m2, P < 0.006), decreased the mean V wave by 26% (from a baseline of 36 ± 12 mmHg, P < 0.004), and decreased pulmonary capillary wedge pressure by 17% (from a baseline of 31 ± 10 mmHg, P < 0.01). Four patients died (1 preoperatively, 1 intraoperatively, 2 within 3 months, and 1 of a noncardiac cause). The four surviving patients have clinically improved from New York Heart Association Functional Class IV to Class II. In these survivors, CI decreased by 15% (P < 0.007) when multisite pacing was turned off during follow‐up. In patients with end‐stage heart failure, multisite pacing may be associated with a rapid and sustained hemodynamic improvement.

Permanent Left Ventricular Pacing With Transvenous Leads Inserted Into The Coronary Veins

This paper describes a preliminary experiment ‐ conducted jointly by 2 centers ‐ of permanent left ventricular pacing using leads inserted by the transvenous route and through the coronary sinus into the cardiac veins of the left ventricle free wall. The aim was to obtain permanent biventricular pacing in a totally endocavitary configuration in pattents with severe LV dysfunction and drug‐refractory heart failure. Two types of leads were used: nonspecific unipolar leads at the beginning of the experiment, followed by leads specifically designed to be used in the coronary sinus in a second step. The electrode could be fitted in an adequate location in 35 of the 47 patients (75.4%), with a 1.15±0.7 V acute pactng threshold and 11.8±5.7 mV R wave amplitude. The success rate was significantly higher with the specific electrodes (81.8% vs 53,3%, p < 0.001). The pacing and sensing thresholds upon implantation were not influenced by the type of lead or by the localization of the cardiac vein that was catheterized (great cardiac vein, lateral vein, postero‐lateral or posterior vein, mid cardiac vein). In contrast, the pacing threshold was significantly lower (0.8 ± 0.2 vs L8 ± 0.8 V; p = 0.002) and the R wave amplitude tended to be greater (13.1 ± 4.5 mV vs 9.3 ± 6.5 mV; p = 0.07) when the tip electrode could be inserted distally into the vein, by comparison with a proximal site near the ostium. At the end of follow‐up (10.2 ± 8.7 months), 34 out of the 35 leads were still fully functional, with a chronic pacing threshold of 1.8 ± 0.7 V and a R wave amplitude of 10.7 ± 6 mV. To conclude, permanent LV pacing via the transvenous route is possible in most patients, with excellent safety and long‐term results.

Long‐term Prevention of Vagal Atrial Arrhythmias by Atrial Pacing at 90/Minute: Experience with 6 Cases

Six patients (5 men, 1 woman) with a history ranging from 3–16 years of resistant vagal atrial arrhythmias were treated by atrial pacing at a rate of 90Jmin. These patients have been followed up for an average of 5.5 years (range 2–11 years) with favorable resutls. The arrhythmias were charactemed by daily or weekly attacks of rypical alrial flutter and atrial fibrillalion occurring mainly or exclusively at night, at rest, or in the digestive periods in otherwise normal hearts of middle‐aged palients (first attack between 25 and 54, mean 40). The arrhythmias werc resistant to quinidinc, and were usually aggravated by digitalis, beta‐blockers and verapamil. Amiodaroneisusually the only effective drug in this syndrome, but was not used before pacing in the 2 first cases, and was in effective in the other 4 cases. Electrophysiologic studies confirmed the absence of sick sinus syndrome, and the close relationship betwecn a relative bradycardia and the onset of the arrhythmia. Atrial pacing alone totally controiled the arrhythmia in 1 palient; amiodarone was used in conjunction with pacing in 3 palients. In 1 patient the improvement was clear but incomplete, and in 1 patient permanent alrial fibrillation occurred shortly afler pacemaker implantalion.

Electrode‐Heart Interface: Definition of the Ideal Electrode

Dans la stimulation à deux chambres, pour garder aux stimulateurs leurs avantages de petite taille, de volume réduit et de longue durée, il est nécessaire de diminuer les seuils de stimulation. Ceci peut être accompli par ľoptimisation de ľinterface électrode‐coeur. Des nouvelles électrodes pourraient réquire les pertes de polarisation; de même, des nouveaux matériaux pourraient être envisagés. Les résultats de ces données doivent être rapportés à stimulation chronique.

Study of Interactions Between Permanent Pacemakers and Electronic Antitheft Surveillance Systems

Interference of electronic antitheft systems (EASs) with pacemakers has been an object of controversy. This study was performed in 204 patients followed by our pacemaker surveillance center. The data from a total of 408‐patient exposures to the EAS were analyzed. The device tested con‐sisted of 129 DDD, 71 VVI, and 4 VDD pacemakers from seven manufacturers. The EAS studied consisted of an “acoustomagnetic” system that emits an intermittent 58‐kHz signal, and a magnetic audio frequency system that emits a continuous 73‐Hz signal. Complete interrogation of the pacemakers was performed be fore and after the consecutive exposure of the patients to both EASs. Electrocardiograms were recorded while the patients were exposed to the magnetic fields of each EAS for up to 30 seconds. One or more EAS interferences occurred in 17% of patients. EAS was observed in 26 (20%) of 729 patients with ODD, 7 (10%) of 71 patients with VVI, and 2 (50%) of 4 patients with VDD pacemakers. Over twice as many in stances of EAS interference were observed with the “acoustomagnetic” system as were with the magnetic audio frequency system. Among pacemakers programmed in the ODD mode, a considerably greater preva‐lence of interference was observed at the atrial versus ventricular level, despite the same programmed sensing polarity in both chambers in all but one case. Sensing anomalies were the most common EAS in‐duced disturbance, and typically lasted for the duration of exposure. In a few instances of pacing inhibi‐tion, the phenomenon was limited to 1 cycle at the onset of EAS exposure. No changes occurred in the programming of the pacemakers, and a single patient experienced palpitation during EAS induced rapid pacing. During exposure to EAS mimicking the normal use of the systems, interference with a variety of pacemakers was relatively common. However, the anomalies observed were transient and the cause of no symptom or device reprogramming. Patients should be advised to not stand unnecessarilv in the close proximity of EASs.

Demand pacemaker arrhythmias caused by intermittent incomplete electrode fracture. Diagnosis with testing magnet.

This report describes how the testing magnet was used to diagnose intermittent and incomplete electrode fracture in two patients with an implanted demand pacemaker. During fixed-rate pacing the interval between two consecutive pacemaker spikes intermittently doubled in length, suggesting that the pulse generator was continuing to fire on time into a transiently disrupted circuit. Attenuated pacemaker spikes occurring at the anticipated time of pacemaker discharge also provided a diagnostic clue. Ventricular electrograms from the defective electrodes registered small false signals.

Reduction in Energy Pacing Thresholds by Overlapping Biphasic Stimulation Versus Conventional Bipolar Pacing

Overlapping biphasic (OLBI) stimulation is a new pacing waveform consisting of two simultaneous monophasic pulses of opposite polarities applied to a bipolar electrode. The goal of this prospective study was to compare, using conventional pacing leads, the acute energy pacing thresholds, measured at 0.5‐ms pulse duration, associated with bipolar versus OLBI (mode 7 and mode 8) pulse delivery. Results: Thirty one leads were tested in 20 patients. Of these leads, 7 (23%) were implanted chronically, 12 (39%) were in atrial positions, and 19 (61%) in ventricular positions. Energy pacing thresholds were significantly lower (‐25.6 ± 25.6 %, P = 0.005) in OLBI mode 8 (1.30 ± 3.96 μJ) compared to bipolar (1.55 ± 4.37 μJ) pacing, regardless of the pacing site or length of service of the leads. In contrast, OLBI mode 7, which has an anodal component, at the tip electrode was associated with higher energy pacing thresholds (3.65 ± 6.48 μJ; +358.3 ± 219.4%, P = 0.002). Conclusions: Mode 8 OLBI pacing is associated with lower acute energy pacing thresholds when used with bipolar leads in contact with the myocardium. OLBI pacing may increase pacemaker longevity by reducing long‐term energy consumption.

The Fifth Decade of Cardiac Pacing

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Pacemaker Miniaturization: A Good Trend?

Many believe that the small size pulse generators have reduced the incidence of local complications such as extrusion and infection of the pocket. Based on this premise, we undertook a retrospective study to determine the impact of miniaturization of the pulse generator size on the local complication rate and longevity. Our database consisted of patients who received 18,245 implanted pacemakers at our institution since since 1969. Fewer than 10% of patients were lost to follow-up. The same physician implanted almost 75% of the devices. Three months after implantation, the output of all pacemakers was programmed (when feasible) to promote maximum longevity with an adequate pacing safety margin. Antibiotic prophylaxis did not affect the results because of our policy of administration to all patients. Since 1987, all patients with devices < 25 cc in volume received antibiotics. The pulse generators were classified into three groups according to volume: Group A: < 10 cc; Group B: 10-25 cc; and Group C: > 25 cc. Since 1987, almost no Group C models have been implanted. A random selection of leads was used, but recently we have used low threshold or high impedance leads routinely when they became available. The size related complication rate (extrusion and infection^) was evaluated in these three groups. Lead related endocarditis or infections secondary to a remote portal of entry