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Biomedical subjects

M J Castellanet

Publications and source records attributed to M J Castellanet.

12 recordsLinked to original sources
PubMed1991

Dacron-woven pacemaker pouch. Influence on long-term pacemaker mobility.

Pacemaker migration can interfere with correct pacing system function and patient comfort. A Dacron pouch has been developed which may prevent these problems. To assess the efficacy of the pouch, we measured various factors of pacemaker mobility in 100 patients after long-term follow-up. The patients were divided into three groups on the basis of their dictated operative reports: group 1, no pouch or anchoring stitch; group 2, pouch only; group 3, anchoring stitch to pacemaker header or pouch. The average age of the study population was 74.3 +/- 11 years. Total follow-up time was 42 +/- 28 months (group I, 53 +/- 32 months; group 2, 36 +/- 23 months; group 3, 34 +/- 25 months). There were no significant differences when pacemakers were measured for movement in the inferosuperior and lateromedial directions, nor was there any difference in the distance between the incision scar and the pacemaker header in any group. There was a significant difference between group 1 and groups 2 and 3 when the degree of tilt of the pacemaker off the chest wall was compared. This was 46 degrees +/- 34 degrees for group 1 and 27 degrees +/- 26 degrees and 26 degrees +/- 27 degrees for groups 2 and 3, respectively (p less than 0.02 for both). These data suggest that the Dacron pouch does not restrict pacemaker mobility parallel to the chest wall during long-term follow-up but does reduce the angle to which the pacemaker can be tilted relative to the chest wall.

Aged↗
PubMed1990

The influence of endocardial electrode fixation status on acute and chronic atrial stimulation threshold and atrial endocardial electrogram amplitude.

UNLABELLED: The endocardial atrial electrogram or "P wave amplitude" (PWA) and pacemaker atrial stimulation thresholds are important parameters determining correct pacing system function. Pacemaker lead fixation mechanism and lead age may negatively influence these parameters. Therefore, we compared acute and chronic PWA and atrial stimulation thresholds in 33 patients with permanent transvenous atrial screw-in leads, follow-up 647 days +/- 297 days; and in 31 patients with nonscrew leads, follow-up 855 days +/- 512 days (P = ns). RESULTS: The PWA differed between the two lead types acutely (1.97 mV +/- 0.8 mV for screw-in versus 2.48 mV +/- 1.1 mV for nonscrew-in leads; P less than 0.05), but not chronically (2.21 mV +/- 0.8 mV vs 2.2 mV +/- 1.2 mV; P = ns). Acute and chronic atrial pacing thresholds did not differ between groups. We also analyzed an early interim PWA in a subgroup of patients (mean 31 days after implantation). The nonscrew fixation group interim PWA was 1.76 mV +/- 0.9 mV versus 2.7 mV +/- 1.2 mV at implant (P less than 0.001). The screw-in lead interim PWA was 2.04 mV +/- 0.9 mV versus 1.97 mV +/- 0.7 mV at implant (P = ns). CONCLUSIONS: (1) A significantly higher endocardial PWA occurs at the time of lead implantation in nonscrew versus screw-in lead groups, but the chronic PWA does not differ between the two groups. (2) A transient but marked early (mean approximately 31 days) attenuation of the PWA occurs only with nonscrew-in leads. (3) Atrial threshold stimulation energies do not differ between the two lead groups acutely or during follow-up.

Aged↗
PubMed1990

Physical determinants of the endocardial P wave.

UNLABELLED: Reliable atrial sensing of intrinsic P wave activity is important to ensure optimal atrial or dual chamber pacemaker function. Various physical factors (e.g., posture, respiration, exercise) may influence P wave characteristics and impair adequate sensing. To investigate this phenomenon, we measured the average of three P wave amplitudes (PWA) and calculated slew rates from telemetered printouts acquired from Pacesetter pacemakers in 32 patients. These measurements were performed in various body positions, with upright exercise and in varying stages of respiration. RESULTS: the mean supine PWA increased on full inspiration (3.56 +/- 1.3 mV versus 3.25 +/- 1.2 mV during quiet respiration, P less than 0.001), and also increased significantly with full expiration. The mean PWA increased on assuming the erect position (3.25 +/- 1.2 mV increasing to 3.49 +/- 1.3 mV, P less than 0.001); in the upright position, the mean erect PWA during quiet respiration was not significantly influenced by the stage of respiration. The mean upright exercise PWA did not differ significantly from the preexercise erect PWA (3.50 +/- 1.2 with exercise, and 3.47 +/- 1.5 before exercise; P = NS). Calculated slew rates were not different lying versus standing. CONCLUSIONS: the mean supine PWA increases significantly at the extremes of respiration and on assuming the erect body position; upright exercise results in no appreciable change in the erect PWA. Atrial sensitivity adjustments based on standard supine testing should be adequate for all body positions.

Adolescent↗
PubMed1990

True incidence of pacemaker syndrome.

Although the purported incidence of pacemaker syndrome according to the literature is only 5%-15%, this is based on a series of patients with VVI pacing. Increasing numbers of studies are being reported in which patients prefer the dual chamber mode despite little benefit being demonstrated on objective testing, suggesting that pacemaker syndrome may be more common than is generally reported. This study was designed to evaluate the reported symptoms in a series of patients programmed to both the VVI and one or more dual chamber modes. Forty unselected patients with dual chamber pacemakers were entered into a blind, randomized trial comparing the symptoms associated with VVI pacing to those associated with dual chamber pacing. Patients were randomized to either VVI or dual chamber pacing. At the end of 1 week, questionnaires rating 16 different symptoms were completed. Blood pressure, LV function, presence of ventriculoatrial conduction, and ability to override the pacemaker were evaluated. The pacemaker was then programmed to the other mode. Overall, 12 of 16 symptoms were significantly worse in the VVI as compared to dual chamber mode. The most highly significant (P less than 0.005) were shortness of breath, dizziness, fatigue, pulsations in the neck or abdomen, cough, and apprehension. Pacemaker syndrome was clinically recognized in 83% of patients paced in the VVI mode with 65% of patients experiencing moderate to severe symptoms. There were no readily identified clinical, hemodynamic, or electrophysiological parameters that predicted which patients would develop pacemaker syndrome. Thus, when patients have an opportunity to experience both pacing modes in close proximity to one another, there is a high incidence of pacemaker syndrome in the VVI mode.

Aged↗
PubMed1989

Variation in P wave amplitude immediately after pacemaker implantation: possible mechanism and implications for early programming.

The P wave amplitude (PWA) plays an important role in determining atrial sensing capabilities. To assess early PWA change, we compared the unipolar PWA in 43 patients at the time of atrial lead placement, measured by a pacing systems analyzer, to the unipolar PWA recorded at the end of pacemaker surgery, from telemetered atrial endocardial electrograms. Individual PWA varied from a decrease of 5.2 mV to an increase of 2 mV (-63% to 267%). In 33 patients with active fixation leads, the implant PWA was 1.96 +/- 0.99 mV versus 2.4 +/- 1.4 mV after surgery. In 11 patients with passive fixation leads, the implant PWA was 2.8 +/- 1.9 mV versus 1.9 +/- 0.8 mV after surgery. The PWA change, measured as the difference between the postsurgical and implant PWA was 0.43 +/- 0.8 mV in active versus -0.86 +/- 1.6 mV in the passive fixation lead groups (P less than 0.05). Considerable change in individual P wave amplitude can therefore occur very early after pacemaker implantation. The direction differs significantly between active (predominantly positive) and passive fixation groups (predominantly negative). These data suggest that an adequate margin of safety is important when initially programming atrial sensitivity, particularly when using passive fixation leads.

Aged↗
PubMed1989

Impaired activity rate responsiveness of an atrial activity-triggered pacemaker: the role of differential atrial sensing in its prevention.

The physiological benefit of rate responsive, single-chamber cardiac pacing is well documented. We studied the activity response of nine atrially placed Activitrax II pacemakers. Seven patients were noted to have an inadequate activity-rate response with maximal pacing rates of 85 to 101 beats/min. Marker Channel analysis revealed that the upper rate timeout was reset by far-field R wave sensing, even when sensing occurred in the atrial refractory period. These 9 pacemakers were tested by atrial sensitivity adjustment for ability to exclude far-field R wave sensing, while preserving P wave sensing. Unipolar implantation data were then examined for predictors of this differential far-R and P-wave sensing. Differential atrial sensing occurred in 4/9 pacemakers (2/2 bipolar in the right atrial appendage; 0/1 bipolar in the coronary sinus; and 4/9 unipolar). An empirically developed index utilizing unipolar implant parameters discriminated outcomes for 8/9 unipolar pacemakers. We conclude that: (1) the rate responsiveness of the atrial Activitrax II pacemaker is limited by far-field R wave sensing even when this occurs during atrial channel refractoriness; (2) reprogramming atrial sensitivity to differentially sensed P and far-field R waves may restore appropriate rate responsiveness; and (3) although a unipolar implant discriminant index may correctly identify adequacy of future rate responsiveness, the atrial application of the Activitrax II pacemaker is cautioned until further validation is forthcoming, particularly when used in unipolar and coronary sinus applications.

Adult↗
PubMed1988

Utility of the atrial endocardial electrogram concurrent with dual-chamber pacing in the determination of a pacemaker-mediated arrhythmia.

A 73-year-old male required a permanent pacemaker for complete heart block. After placement of the dual-chamber pacemaker, the patient developed random, repetitive ventricularly paced coupling at the upper rate limit. The diagnosis made from the surface electrocardiography was one of ventricular tracking of occult (T wave obscured) atrial ectopic activity. Examination of the telemetered atrial electrogram (EGM) revealed a diagnosis of intermittent far-field atrial sensing of the terminal ventricular depolarization. The value of obtaining an atrial electrogram during dual-chamber pacing is discussed.

Aged↗
PubMed1979

Predicting coronary artery disease with treadmill stress testing: changes in R-wave amplitude compared with ST segment depression.

Coronary angiograms and treadmill stress tests were reviewed independently in 108 nonconsecutively selected cases. There were 16 patients (15%) with infarcts on ECG. Changes in R-wave amplitude and ST segments during exercise were evaluated to determine the sensitivity and specificity of each as a predictor of coronary artery disease (CAD). ST segment changes had a sensitivity of 49%, and a specificity of 74%. The sensitivity increased to 55% when infarcts were excluded. R-wave amplitude changes had a sensitivity of 68% and a specificity of 84%. The sensitivity increased to 78% when infarcts were excluded. An index formed by the sum of the change in R-wave amplitude and the magnitude of ST segment change yielded a sensitivity of 76% and specificity of 78%. The sensitivity increased to 84% when infarcts were excluded. There was no statistical difference between specificities for each criteria. Of those patients with an R-wave amplitude decrease, 69% had no coronary artery atherosclerosis, while 31% had significant lesions. Of those patients with no change or an increase in R-wave amplitude, 83% had coronary artery atherosclerosis, while 17% were normal. Of the 83% with coronary artery atherosclerosis, 81% had two and three vessel disease, while only 19% had single vessel disease. No change or an increase in R-wave amplitude during treadmill stress testing is a more reliable indicator of CAD in our laboratory than ST segment changes.

Adult↗
PubMed1978

Significance of changes in R wave amplitude during treadmill stress testing: angiographic correlation.

Coronary angiograms and treadmill stress tests were reviewed in 89 patients. Changes in R wave amplitude were measured in the control and immediate postexercise periods. Of 45 patients with normal coronary arteries, 41 (91 percent) had a decrease in R wave amplitude (P less than 0.01); 3 (7 percent) had an increase in amplitude, including 2 with abnormal left ventriculograms. The remaining patient (2 percent) had abnormal wall motion but no change in R wave amplitude. Among the 44 patients with significant coronary artery disease (70 percent or greater luminal narrowing in one or more vessels), R wave amplitude increased after exercise in 26 (59 percent) with more severe coronary artery disease. R wave amplitude decreased in 18 patients (41 percent) with normal or minimally abnormal resting ventriculograms and less severe coronary artery disease (P less than 0.01). Changes in R wave amplitude reflect ventricular function, an increase in R wave amplitude reflecting more severe dysfunction and severe coronary narrowing. A decreased R wave amplitude indicates normal or minimal dysfunction and is strongly associated with normal coronary angiograms.

Adult↗
PubMed1978

Comparison of S-T segment changes on exercise testing with angiographic findings in patients with prior myocardial infarction.

Ninety-seven patients with a prior transmural myocardial infarction who underwent coronary angiography and treadmill stress testing were studied retrospectively to assess the reliability of the exercise electrocardiogram in detecting additional disease in patients with a prior infarction. In patients with a previous inferior wall infarction, the S-T response to the treadmill stress test had a high degree of sensitivity (87 percent) and specificity (90 percent) in detecting additional significant coronary artery disease. However, in patients with a previous anteroseptal wall infarction, the S-T response had much less sensitivity (52 percent), but the degree of specificity remained high (90 percent). In this group a positive test suggested the presence of ischemia in the lateral or inferoposterior region of the myocardium, or both. A negative S-T response was of little value in distinguishing among groups of patients with single or multiple vessel coronary artery disease. The presence of an anterior ventricular aneurysm is most likely responsible for this low sensitivity rate because it generates an opposing force to the ischemic vector, thereby cancelling the S-T segment changes and producing a false negative treadmill stress test. The resting surface electrocardiogram proved useful in predicting a false negative exercise test. The presence of Q waves in the precordial leads extending to lead V4 or beyond decreased the sensitivity rate of treadmill stress testing to 33 percent.

Adult↗
PubMed1978

Evaluation of R wave amplitude changes versus ST-segment depression in stress testing.

Exercise ECGs and coronary angiograms were reviewed in 266 patients (81 normals and 185 with significant coronary artery disease). Thirty-three false positive and 96 false negative ST responses to stress testing were purposely chosen to determine if the R wave could reduce the number of false ST responses. R wave amplitude changes were measured in the control and in the immediate postexercise period. An increase or no change in R wave was taken as evidence of an abnormal response, while a decrease in the R wave was a normal response. The sensitivity by ST segment was 48% and the specificity was 59%. These values were low because of the large number of false positive and negative ST responses in the study. It was our purpose to determine if these lowered values could be significantly improved by the R wave. Using R wave criteria, the sensitivity was 63% (P is less than 0.01) while the specificity was 79% (P is less than 0.01). The sensitivity and specificity of stress testing can be significantly improved using R wave changes.

Coronary Angiography↗