Contribution of a pacemaker bradycardia detection algorithm in the study of patients with carotid sinus syndrome.

While carotid sinus syndrome (CSS) is often suspected as a cause of syncope in the elderly, whether it represents an indication for cardiac pacing may remain uncertain. Bradycardia algorithms included in pacemakers are now able to establish a precise relationship between spontaneous asystole and occurrence of symptoms and strengthen the indication for permanent pacing. This study included seven men and three women (70.5 +/- 7.3 years of age) who, over an average period of 54.1 +/- 17 months, had suffered from syncope (12.6 episodes/patient) and presyncope (11.2 episodes/patient) attributed to pure cardioinhibition (2 patients) or mixed CSS (8 patients). Other sources of symptoms were excluded by thorough clinical evaluations, including Holter monitoring, echocardiography, and electrophysiological testing. All patients received a CHORUS 6234 pacemaker, the memory of which includes a dedicated bradycardia detection algorithm capable of storing atrial and ventricular chains, and date and time of the last ten pauses and/or bradycardic events. After a initial period of 14.7 +/- 8 months, during which symptoms were suppressed, the bradycardia algorithm was activated. From then on, a cumulative increase in the number of patients presenting with diurnal pauses was measured (1 month, n = 0; 3 months, n = 6; 9 months, n = 7; 2 years, n = 8). Fourteen episodes of diurnal asystole were recorded. The mean duration of the longest episodes of spontaneous ventricular standstill was 6,319 +/- 1,615 ms and was due to sinoatrial block (n = 7), atrioventricular block (n = 5), and a combination of both (n = 2). In conclusion, activation of the CHORUS bradycardia algorithm allowed confirmation of the appropriateness of permanent pacing in a majority of patients suffering from CSS.

Reliability of single-lead VDD atrial sensing and pacing during exercise.

If atrial sensing ability of a single-lead VDD pacemaker is well accepted at rest, the detection quality by atrial floating electrodes remains less recognized during exercise. The aim of this study was to verify, during treadmill test and a continous telemetry, the atrial tracking performance using four different leads technologies. From November 1994 to July 1997, 21 patients (71.3 +/- 6.3 years old, 7 female, cardiopathy: 57%) were paced for isolated high degree (permanent: 13, paroxystic: 8) AV block. The implanted devices were the Vitatron Saphir/Brillant lead (13 patients), Intermedics Unity/425/04-13 lead (5 patients), Pacesetter Addvent (2 patients), and Biotronik Eikos (1 patient). The acute atrial signal amplitude was 1.66 +/- 0.75 mV. The treadmill test used the chronotropic assessment exercise protocol after pacemaker reprogramming to detect atrial undersensing (AV delay < or = 120 ms, no hysteresis, no flywheel, upper rate increase). The mean delay was 31.1 weeks (range 1-100). The testing duration was 6.1 +/- 2.3 minutes, the number of steps was 3.3 +/- 1.3 per patient, and the peak exercise rate was 135 +/- 19 beats/min. At rest, complete atrial tracking was complete in 90% of the patients, and during testing in only 23.8% of the patients, while AV synchronization > 95% was present in 57.1%, > 90% in 71.4%, and > 85% in 90.4% of patients (Vitatron 13/13, Intermedics 3/5, Biotronik 1/1, and Pacesetter 1/2). During the recovery period synchronization was always > 95%. The mean P wave amplitude at rest was 1.1 +/- 0.5 mV; during the first step, 1.04 +/- 0.61 mV; second step, 0.94 +/- 0.53 mV; third step, 0.82 +/- 0.58 mV; fourth step, 0.67 +/- 0.39 mV; and during recovery, 1.13 +/- 0.67 mV. The mean P wave decrease signal at peak of exercise is 0.21 mV (from -1.31 to +0.5). In fact, P wave variations have several patterns: a decrease was measured in 7 patients, an increase in 2 patients, and no significant change in 7 patients. Single-lead VDD P wave identification during exercise was almost accurate. However, often there was progressive lowering of atrial sensing with transient loss of AV synchrony.

Wavelength and atrial vulnerability: an endocavitary approach in humans.

If atrial vulnerability parameters are well defined, wavelength (WL) measurement (conduction velocity x refractory period), has never been assessed through an endocavitary electrophysiological exam. We investigated 30 patients (14 female, mean age 63.4 +/- 13 y.o.), 10 with paroxysmal atrial fibrillation (PAF group), 10 with ischemic cerebral injury (ICI group) by comparison with 10 controls (C group). The upper to lower right atrium conduction time and velocity were measured in the right atrium with a decapolar electrode catheter applied along the free wall. Others parameters correlated to atrial excitability were also taken into account: effective (ERP) and functional refractory periods (FRP); spontaneous or paced atrial electrogram (A1) or extrastimulated atrial electrogram (A2) widths, ERP/A2 ratio, provocative atrial testing. Measurements were taken in sinus rhythm and in 600-460 ms paced cycle lengths. If ERP, FRP, A1 widths are the same in the 3 groups, PAF and ICI groups have a significant increased conduction time and lower conduction velocity, leading to a shorter A1 WL during 600 and 460 ms paced rhythms (p < 0.05) and A2 WL during 460 ms paced rhythm. The provocative testing was positive in 60% of PAF and ICI groups, and there is a significant correlation between arrhythmia induction and 600 ms A1 WL or 460 ms A2 WL. This electrophysiological study suggests the possibility of an approach in humans of wavelength concept and proves the presence of correlation between a short wavelength and atrial spontaneous or induced arrhythmias. A no-arrhythmia band (A1 WL > 17 cm during 600 ms paced rhythm, A1 WL > 16 cm or A2 WL > 12 cm during 460 ms paced rhythm) and a fibrillation-band (A1 WL < 12 cm during 600 and 460 ms pacing, A2 WL < 7 cm during 460 ms pacing) can be defined. Therefore, the ICI group has the same atrial pattern as the AF group.

Prospective evaluation of high-dose or low-dose isoproterenol upright tilt protocol for unexplained syncope in young adults.

The sensitivity of the passive head-up tilt test (HUT) in the evaluation of unexplained short-lasting syncope in young adults remains insufficient. The infusion of isoproterenol was proposed to improve the benefit. To evaluate the sensitivity-specificity relationship during isoproterenol dosing, we studied 76 young adults (aged 20.9 +/- 1.7 years) (group S) with recurrent (mean 3.8 +/- 1.6) losses of consciousness that remained unexplained after clinical and noninvasive assessment and 35 young healthy volunteers (aged 22.6 +/- 2.7 years) (group V). Subjects underwent either passive HUT (45 min, 60 degrees without drug dosing for 48 subjects in group S (S1) and 17 in group V (V1), or HUT with isoproterenol infusion at progressive doses (2 then 5 micrograms/min) after 30 minutes of passive tilting for 28 patients in group S (S2) and 18 in group V (V2). During passive HUT, the test was positive (asystole, bradycardia, or fall in systolic blood pressure) in 2 of 17 (11.8%) patients in group V1 and in 7 of 48 (14.6%) in group S1 before 30 minutes, and in 3 of 17 (17.6%) in group V1 compared with 10 of 48 (20.8%) in group S1 at the end of the 45-minute infusion, with no difference in delay before the appearance of a positive result. During HUT with isoproterenol dosing, the test was positive in 2 of 18 (11.1%) patients in group V2 and in 18 of 28 (64.2%) in group S2 before 45 minutes (2 micrograms/min; p < 0.01) in 7 of 18 (38.8%) in group V2 compared with 24 of 28 (85.7%) in group S2 before 60 min (5 micrograms/min; p < 0.01). In both cases the mean delay in evoking a positive response was significantly shorter. No asystolic response was observed in the volunteers regardless of the protocol used. The most characteristic response to isoproterenol injection was the appearance of a junctional escape rate with a fall in systolic blood pressure (61.5% of subjects in group S2). The infusion of isoproterenol considerably improves the sensitivity of the HUT with satisfactory specificity if low doses are used (< 3 micrograms/min). These results support the use of HUT with isoproterenol in the evaluation of unexplained syncope in young adults.

[Multifactor prevention of endocarditis and cardiac pacemakers. A prospective study apropos of 207 patients]. / Prévention polyfactorielle des endocardites et stimulateurs cardiaques. Une étude prospective à propos de 207 patients.

Infections after cardiac pacemaker implantation are rare (0.13 to 12.6%) but potentially severe complications. Staphylococcus is the genus most frequently isolated (72 to 100% of cases). The use of systematic prophylactic antibiotics remains controversial. From November 1991 to October 1993, 207 consecutive patients were submitted to a series of measures designed to reduce the risk of infection: a) intravenous bolus injection of Cefamindole, 15 minutes before implantation, b) cutaneous disinfection with iodinated polyvindone, c) injection of an ampoule of rifampin before closure of the pacemaker in the pouch, d) absence of drainage system. Patients were predominantly female (60.9%), with a mean age of 77 +/- 10 years, frequently suffering from heart disease (53.8%). The indication for implantation was atrioventricular block (39.7%), carotid sinus syndrome (27.5%), atrial arrhythmia (27.5%), resection of the node-His tract (5.3%). This procedure corresponded to the first implantation in 88.4% or replacement of a previous pacemaker in 11.6% of cases and the pacing mode was single-chamber (38.4% or replacement of a previous pacemaker in 11.6% of cases and the pacing mode was single-chamber (38.7%), or double chamber (61.3%). The mean duration of the procedure was 51.5 min +/- 30 min. The mean follow-up was 12.7 +/- 5 months. The overall mortality was 14% (11 cases of cardiac failure, 6 sudden deaths, 4 cerebrovascular accidents, 4 cases of pneumonia, 4 neoplasms). Only one infectious problem (endocarditis, i.e. 0.48%) was observed.

[Characteristics and influence of different clinical forms on the development and prognosis of carotid sinus syndrome. Apropos of 215 cases]. / Caractéristiques et influence des différentes formes cliniques sur l'évolution et le pronostic des syndromes du sinus carotidien. A propos de 215 cas.

The carotid sinus syndrome is a well-known cause of syncope: the cardio-inhibitory forms are the easiest to diagnose and probably the easiest to treat. However, the vasodepressive forms are as common but their outcome is mainly unknown. Eight hundred and fifty-three patients underwent endocavitary electrophysiological studies with invasive blood pressure measurement for unexplained syncope between October 1984 and January 1990. A carotid sinus syndrome was diagnosed in 215 cases. Fifty-two patients (24.2%) had a cardio-inhibitory form (ventricular standstill > or = 3 s during carotid sinus massage), 40 (18.6%) had a pure vasodepressive form (isolated fall of systolic blood pressure > 50 mmHg during massage) and 123 patients (57.2%) had a mixed form. The average age was 74.1 +/- 9.7 years with no difference between the different forms. A number of parameters was different on the cardio-inhibitory and vasodepressive forms: the number of men (75.6 vas 24.4%; p < 0.05) and the number of syncopes (83.3 vs 60%; p < 0.02) were greater in the cardio-inhibitory form; the vasodepressive forms were more often associated with a history of transient ischaemic attacks (15 vs 0%), a poor cardiovascular status (hypertension: 47.5 vs 15.7%; p < 0.01), coronary artery disease (47.5 vs 25.5%; p < 0.05), cardiac failure (27.5 vs 11.7%; p < 0.05), induction of sustained supraventricular tachycardia (50 vs 23.5%; p < 0.05) and a greater pacemaker effect (53.6 vs 34.8 mmHg; p < 0.01); of the 191 patients (84.9% of the population) followed up for an average of 21.2 months, 168 received treatment: implantation of a cardiac pacemaker in 108 patients, reduction of antihypertensive and/or potentially bradycardia-inducing drugs in 30 patients, prescription of antiarrhythmic therapy, in 30 patients.(ABSTRACT TRUNCATED AT 250 WORDS)