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Biomedical subjects

R G Hauser

Publications and source records attributed to R G Hauser.

At least 37 records · Page 2Linked to original sources
PubMed1984

Techniques for improving cardiac performance with implantable devices.

A variety of pacing techniques are available to improve cardiac performance in patients who have bradyarrhythmias. These approaches include the preservation of AV synchrony and rate responsiveness, whereby pacing rate is varied according to some physiologic marker such as the atrial rate. New rate responsive pacemakers utilize other sensors to govern pacing rate and these units may monitor QT interval duration, respiratory rate, activity, venous oxygen saturation, temperature, or pH. Additional sensors are presently being investigated and prototype stroke volume and pressure monitoring devices should be available in the near future. All of these approaches require clinical evaluation and their eventual widespread application must be preceded by thorough studies of benefit, risk, and cost.

Bradycardia↗
PubMed1983

Multiprogrammable cardiac pacemakers. Applications, results, and follow-up.

More than 50 percent of patients with implanted pulse generators live more than 5 years and 35 percent survive beyond 10 years. For such patients, programmable pulse generators offer the flexibility to safely prolong battery life and to alter pacing function based on clinical and electrophysiologic requirements. Further, the potential to diagnose and treat pacing system malfunctions noninvasively in the future may significantly reduce the discomfort, inconvenience, and cost of reoperation. Physicians should select programmable models based on proved system reliability, clinical needs, and the availability of supervised follow-up programs. Finally, the safe and efficacious application of programmable pulse generators requires knowledge of pacing electrophysiology and techniques, and a thorough acquaintance with the operating characteristics of the systems selected for implantation.

Angina Pectoris↗
PubMed1983

The electrocardiography of AV universal DDD pacemakers.

The interpretation of DDD pacemaker electrocardiograms may be performed using basic techniques and by applying the fundamental principles of noncompetitive pulse generator sensing, timing, and pacing characteristics. Precise knowledge of individual model specifications and programmable parameters is mandatory if physicians are to avoid the consequences of misinterpretation. Manufacturers must provide adequate information regarding their DDD models, and the medical community should develop more sophisticated surveillance methods for following these pacemakers.

Adolescent↗
PubMed1983

Normal electrophysiological findings in a patient with symptomatic intermittent advanced atrioventricular block.

This report describes an otherwise healthy young woman who presented with syncope during episodes of advanced atrioventricular (AV) block. The His bundle recordings during normal sinus rhythm and atrial and ventricular pacing were normal. Carotid sinus massage produced no abnormality. Subsequently, the patient received a permanent pacemaker and has been free of symptoms. Intermittent advanced AV block has been observed on follow-up electrocardiograms. This unique case demonstrates a potential limitation of routine electrophysiologic investigation.

Adult↗
PubMed1983

Quantitative analysis of the high-frequency components of the terminal portion of the body surface QRS in normal subjects and in patients with ventricular tachycardia.

Quantitative analysis of the high-frequency components of the terminal portion of the surface QRS was performed in 42 normal subjects (group 1, ages 18-67 years, mean +/- SEM 34.7 +/- 2.2 years) and in 12 patients with symptomatic, sustained ventricular tachycardia (VT) (group 2, ages 48-76 years, mean 59 +/- 2.3 years). Signal averaging and high-pass, bidirectional digital filtering were used for analysis. The total duration of the QRS, the duration of the low-amplitude signals (less than 40 microV) in the terminal portion of the QRS and the amplitude of the signals in the last 40 and 50 msec of the QRS were measured at filter settings of 25 and 40 Hz. Reproducibility of the measurements was tested in 15 normal subjects by comparing results obtained from two consecutive recordings. Significant differences were found between normal subjects and VT patients for all four indexes at both 25- and 40-Hz filters. Specific values for each of the indexes were identified at the 40-Hz filtering, which could separate normal subjects from VT patients (20 microV for the amplitude of last 40 msec; 30 microV for the amplitude of last 50 msec; 120 msec for the total duration; and 39 msec for the low-amplitude signal of the filtered QRS). Using these values for the four indexes, respectively, 90%, 98%, 100% and 90% of the normal subjects and 83%, 83%, 58% and 83% for the VT group were correctly classified. The results show that the high-frequency analysis of the signal-averaged body surface QRS is a reliable, reproducible, noninvasive method for distinguishing patients with VT from normal subjects.

Adolescent↗
PubMed1982

Unipolar sensing abnormalities: incidence and clinical significance of skeletal muscle interference and undersensing in 228 patients.

Compared to bipolar lead configurations, unipolar pacing systems presumably enhance sensing of cardiac electrical events but are ore susceptible to electrical interference, including skeletal myopotentials. The incidence and clinical significance of oversensing and of undersensing by unipolar R-wave inhibited pacemakers in 228 patients were assessed by 24-hour Holter monitoring and/or by pectoral muscle exercises. Overall, 38% of patients exhibited oversensing and false inhibition due to skeletal myopotentials. Symptoms due to oversensing occurred in 14% of patients and 58% of these required corrective intervention. The presence of silastic coating on the pulse generator had no effect on the sensing of myopotentials. In addition, the incidence of undersensing as assessed by Holter monitoring was 17% despite adequate implantation R wave amplitudes. Thus, oversensing remains a major clinical problem when using unipolar pacemaker systems and their use has not eliminated undersensing.

Electrophysiology↗
PubMed1982

Successful management of pacing system malfunctions without surgery: the role of programmable pulse generators.

The value of programmable pulse generators for correcting pacing system malfunction without surgical revision was assessed in 293 patients. Twenty-five patients (8.5%) developed malfunctions from one day to 38 months after implant. Of these, 16 or 64% were successfully managed by programming alone, while nine patients required lead repositioning or a new lead. The majority (75%) of isolated pacing and sensing malfunctions were corrected by programming, but programming restored normal pacing function in only one of five patients who had combined sensing and pacing malfunctions which appeared early after pacemaker insertion. We conclude that programmable pulse generators are particularly useful for managing isolated pacing or sensing malfunctions. However, programmability is not a substitute for careful lead placement.

Bradycardia↗
PubMed1982

Noninvasive identification of initial site of abnormal ventricular activation by least-square phase analysis of radionuclide cineangiograms.

Least-square phase analysis (LSPA) of radionuclide cineangiograms demonstrates the sequence of onset of inward ventricular movement noninvasively. To validate the method and explore its ability to identify abnormal initial sites of ventricular activation, LSPA was applied to 14 patients with pacemakers (one with electrodes in two locations) (group 1) and three patients with recurrent ventricular tachycardia (VT) (group 2) who had undergone electrophysiologic endocardial mapping. The segment in which the site of initial ventricular activation was located was correctly identified in 13 of 15 paced studies and in two of three group 2 patients during VT. Pacing increased the duration of spread of onset of inward ventricular movement, and the duration of spread of onset correlated well with the duration of the QRS (r = 0.80). The sequence of onset of inward ventricular movement during VT was similar to the sequence of depolarization in all three group 2 patients. These preliminary results suggest that the sequence of onset of ventricular contraction as depicted by LSPA is a valid representation of the actual contraction sequence and that LSPA or radionuclide cineangiography correctly identifies abnormal sites of initial ventricular activation.

Arrhythmias, Cardiac↗
PubMed1981

Dual mode sensing by a variable cycle ventricular synchronous pulse generator.

When the Intermedics Cyberlith pulse generator is operating in its R-wave synchronous (VVT) mode, sensed events may trigger stimulus pulses or inhibit the output circuit. This dual mode response to sensed signals is the result of a variable timing cycle which includes an inhibit alert period (IAP) as well as a synchronous alert period (SAP). Sensed events occurring during the IAP result in inhibition of stimulus pulse output and resetting of the timing circuit. Consequently, during a continuous ECG rhythm strip one may observe synchronous and inhibited sensing responses and slowing of the pacing rate below the programmed rate of the pulse generator.

Action Potentials↗