The aim of this study was to assess the feasibility of a cephalic vein cutdown and venography technique for implantation of a pacemaker or ICD and to determine the causes of failure of cephalic vein cutdown. In consecutive patients who underwent pacemaker or ICD implants, a modified cephalic vein guidewire technique was performed. This technique was attempted in 289 pacemaker implants and 26 ICD implants (155 men, 160 women; mean age 74 +/- 10 years). The success rate for implantation of a single chamber and a dual chamber device by using this technique alone was 84% (54/64) and 74% (185/251), respectively (P = 0.10). In an additional 7% of patients with dual chamber implant, the cephalic vein can be used for passage of the ventricular lead. A cephalic venogram was required in 82 patients and facilitated the passage of the guidewire in 62 (79%) of them. No complication related to vascular access was observed with this technique. This technique failed in 54 (17%) of 315 patients due to (1) failure of cephalic vein isolation (48%), (2) venous stenosis (24%), or (3) venous torturosity or anomalies (28%). There were no significant differences in the patient's age, sex, type of device, and the fluoroscopic time for lead placement between patients with or without successful lead placement using this technique (all P > 0.05). In conclusion, a simple modification of the cephalic vein guidewire technique together with venography has facilitated the placement of leads during pacemaker and ICD implant. This technique is safe and applicable in the majority of patients and avoids the risk of subclavian puncture.

AF with a fast ventricular response may cause ventricular mechanical impairment, though whether short-lasting AF with satisfactory rate control may affect ventricular function is unknown. This study investigated if prompt cardioversion by an implantable atrial defibrillator (IAD) may prevent left (LV) and right ventricular (RV) systolic and diastolic dysfunction. Ten patients (mean age 61 +/- 9 years, 8 men) with paroxysmal AF without structural heart disease who received an IAD were studied by echocardiography and tissue Doppler imaging (TDI) for both ventricles. Measurements were made during baseline sinus rhythm and at 1-minute, 20-minute, 4-hour, and 1-week postcardioversion of an episode of spontaneous AF. The occurrence of AF and the ventricular rate were monitored at 2-hour intervals by the device. There were 50 episodes of AF with a mean duration of 8.8 +/- 8.9 days (2 hours to 37 days). There was no difference in M-mode measured LV fractional shortening and ejection fraction between baseline sinus rhythm and after cardioversion. However, the TDI derived myocardial systolic velocity (TDI-S) was significantly lower at 1-minute postcardioversion and was normalized at 1 week in both LVs (baseline: 5.7 +/- 1.8, 1 minute: 4.2 +/- 1.0, 20 minutes: 4.3 +/- 0.9, 4 hours: 4.8 +/- 1.0, 1 week: 5.5 +/- 1.8 cm/s; P < 0.005 when comparing 1 minute and 20 minutes to baseline; P < 0.05 when comparing 4 hour to baseline) and RV (baseline: 10.4 +/- 2.1, 1 minute: 7.8 +/- 1.4, 20 minutes: 8.1 +/- 1.2, 4 hours: 9.2 +/- 1.5, 1 week: 10.0 +/- 2.0 cm/s; P < 0.005 when comparing 1 minute, 20 minutes, and 4 hours to baseline). For diastolic function, transmitral Doppler study showed a decrease in early filling velocity at 1 minute (P < 0.05) and 20 minutes (P < 0.005), which was normalized at 4 hours. There was no change in transtricuspid Doppler flow. However, TDI derived myocardial early filling velocity was decreased in the LV (baseline: 6.0 +/- 2.8, 1 minute: 5.4 +/- 2.3, 20 minutes: 5.4 +/- 2.1, 4 hours: 6.1 +/- 2.2, 1 week: 5.8 +/- 1.7 cm/s; P < 0.05 when comparing 1 minute and 20 minutes to baseline) and RV (baseline: 8.9 +/- 3.5, 1 minute: 7.9 +/- 3.3, 20 minutes: 8.1 +/- 3.3, 4 hours: 8.5 +/- 2.9, 1 week: 8.4 +/- 3.5 cm/s; P < 0.05 when comparing 1 minute to baseline). AF of a longer duration (> 48 hours) resulted in a more depressed TDI-S in LV (> 48 hours: 4.2 +/- 1.0, < or = 48 hours: 5.3 +/- 1.3 cm/s; P < 0.01). Shocks in sinus rhythm did not affect any of the above echocardiographic parameters. Therefore, despite adequate rate control, short-lasting AF impairs systolic and diastolic function in both ventricles, which improves gradually after cardioversion. Early restoration of sinus rhythm by an IAD minimizes ventricular dysfunction. TDI is a sensitive tool to assess early systolic and diastolic dysfunction.

Automatic mode switching (AMS) prevents tracking of paroxysmal atrial fibrillation (AF) in dual chamber pacing. The correct detection of AF can be affected by the programmed atrial sensitivity (AS). We prospectively studied the relationship between AS, AF undersensing, and AMS, using unfiltered bipolar intracardiac atrial electrograms recorded from 17 patients during sinus rhythm (SR) and in AF. Overall, 780 rhythms were recorded and replayed onto three dual chamber pacemaker models using different AMS algorithms (Thera DR 7940, Marathon DDDR 294-09, and Meta DDDR 1254), and the ventricular responses were measured. AS was randomly programmed in steps from the highest available AS to half of the mean atrial P wave amplitude (PWA), and the percentage of appropriate AMS responses (defined as a ventricular pacing rate at the expected AMS mode) were recorded. AMS efficacy was related to the programmed AS settings in an exponential manner. At low AS settings, a higher percentage of tests were associated with absence of, or with intermittent AMS and tracking of AF, whereas at higher AS, oversensing of noise during SR occurred. An optimal AS measured approximately 1.3 mV, representing about one-third of the PWA measured during SR, although oversensing of SR and undersensing of AF continued to occur in 14% of tests and time, respectively, due to the high variation in PWA during AF. Thus, a fixed AS cannot eliminate AF undersensing without inviting noise oversensing, suggesting the need for automatic adjustments of AS, or the use of a rate-limiting algorithm to prevent rate oscillation during intermittent AF sensing. In conclusion, AMS functions of existing pacemakers were significantly limited by the undersensing of AF and oversensing of noise. Proper adjustment of the AS is important to enable effective AMS during AF.

LEUNG, S.-K., ET AL.: Automatic Optimization of Resting and Exercise Atrioventricular Interval Using a Peak Endocardial Acceleration Sensor: Validation with Doppler Echocardiography and Direct Cardiac Output Measurements. Peak endocardial acceleration (PEA) measured by an implantable acceleration sensor inside the tip of a pacing lead reflects ventricular filling and myocardial contractility. The contri bution of the plateau phase of PEA as an indicator of optimal ventricular filling, hence of the appropriate atrioventricular interval (AVI) at rest and during exercise, was studied in 12 patients (age 69 ± 6 years) with complete A V block anda PEA sensing DDDR pacemakers (Living 1 Plus, Sorin Biomedica). At a mean resting heart rate of 79 ± 15 beats/min, the mean AVI optimized by PEA versus Doppler echocardiogra phy (echo) were identical (142 ± 37 vs 146 ± 26 ms, P = 0.59). During submaximal exercise at a mean heart rate of 134 ± 6 beats/min, AVI optimized by PEA was 135 ± 37 ms. Cardiac output at rest, measured by the C0 2 rebreathing method, was comparable with AVI determined by echo versus PEA (4.3 ± 2.9 and 3.7 ± 2.4 L/min, respectively), and increased to the same extent (8.0 ± 3.9 vs 8.3 ± 5.2 L/min) during submaximal exercise. In patients with AV block, AVI automatically set by PEA was comparable with AVI manually optimized by Doppler echocardiography and was associated with comparable exercise induced hemodynamic changes. (PACE 2000; 23[Pt. II]:1762-1766) atrioventricular interval, peak endocardial acceleration, Doppler echocardiography, cardiac output