Innovations in pacing technology, which include the addition of rate-responsive features to programmable pacemakers, can improve the quality of life of patients suffering from sick sinus syndrome. Among the strategies providing rate-adaptive cardiac pacing, the most attractive is the physiological restoration of closed-loop chronotropic control. This paper describes how autonomic nervous system (ANS) control information is extracted from dynamic measures of myocardial contractile performance obtained from unipolar conductance measurements using the stimulation electrode in the right ventricular cavity. The pacemaker uses the ANS information to modulate pacing rate and restore normal physiological control of heart rate. A new algorithm, regional effective slope quantity (RQ), for isolating the ANS signal was developed. The resulting signal, ventricular inotropic parameter (VIP), is a normalized parameter proportional to the strength of the ANS inotropic signals to the myocardium. The efficacy of the ANS control concept was evaluated in multi-centre studies. Patients with AV block and VIP-controlled pulse generators performed defined exercise protocols. The ANS-controlled pacing rate and the spontaneous sinus rate were closely correlated. Blood pressure and subjective patient reports further indicated that good control of the cardiovascular circulation was achieved.
A multicenter clinical study is presented, which focuses on the reestablishment of closed loop cardiac control in patients with chronotropic insufficiency. Using the information about sympathetic tone contained in the myocardial contractility, it is possible to reconnect the heart rate to the physiological control mechanisms. Intracardiac impedance is measured with the ventricular electrode and the ventricular inotropic parameter (VIP) is derived from that. The VIP serves directly as input to the control of heart rate by the pacemaker. Over 200 patients have received autonomic nervous system (ANS) controlled pacemakers. The patient-pacemaker system was investigated in different ways. This included standard exercise tests, long-term studies of every day activities over 24 hours, psychological, and pharmacological challenges. To prove the validity of the approach we specifically looked at (1) the appropriateness of changes in paced heart rate with sympathetic tone during exercise, (2) the correlation between heart rate and sinus rate, if detectable, and (3) the correlation between the echocardiographically determined preejection period (PEP) and the VIP controlled heart rate.
Investigations by Jones and Kahn (1Q64) have shown that patient attitudes toward mental illness and treatment are related to the social class level of the patient, which in turn is related to the type of treatment assigned. Response to treatment as a function of attitude toward hospitalization has had little previous investigation. The present study aimed at determining the relationship of such patient attitudes to aspects of hospital course, such as response to treatment and length of stay, to patient demographic factors, and to attitudes of ward personnel.Consecutive admissions to a psychiatric ward were administered the CPH Factor Attitude Scale (Kahn, Jones, Macdonald, Conners, & Burchard, 1963) upon admission and prior to discharge. The SI male veterans had a mean age of 38.9 years, mean education of 12.2 years, and mean hospital stay of 26.94 days. Modal diagnosis was schizophrenia. Response to treatment was measured by ratings of attendance, participation, benefit from therapy, and overall progress, obtained from the principal therapist of each therapy at discharge. Ratings were correlated with attitude and demographic factors. A comparison of the initial patient attitude with that of the ward personnel was carried out.Patient attitude correlated significantly, but at low magnitudes, with length of hospitalization on three of the five attitude factors. Patients with the most authoritarian view of the hospital, and those with the most negative view of hospitalization, tended to stay the longest. However, patients 1 Reprints and an extended report of this study may be obtained without charge from
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