Comparison of Ventricular Function in Atrial Rate Adaptive Versus Dual Chamber Rate Adaptive Pacing During Exercise

The hemodynamic effects of two different pacing modes—rate adaptive atrial (AAIR) versus dual chamber (DDDR) pacing—were assessed in 12 patients with DDDR pacemakers during upright bicycle exercise first-pass radionuclide angiography using a multiwire gamma camera with tantalum-178 as a tracer. All patients had sinus node disease with intact AV conduction. Patients exercised to the same heart rate in random order in these two different pacing modes, AAIR and DDDR with AV delay (of 100 msec) selected to maintain 100% ventricular capture. Cardiac output in creased significantly above baseline values during exercise in both pacing modes: 154 ± 41% (mean ± SEM, P = 0.002) with AAIR, versus 95 ± 24% (P = 0.004) with DDDR (P = NS between the two modes). The peak filling rate, likewise, increased in both pacing modes (2.3 ± 0.21 end-diastolic volumes/sec to 3.8 ± 0.31 end-diastolic volumes/sec in AAIR [P = 0.0004] and 2.2 ± 0.18 end-diastolic volumes/sec to 3.4 ± 0.27 end-diastolic volumes/sec in DDDR [P = 0.0008]). LV ejection fraction was normal at rest (60 ± 4%, SEM) and did not significantly change with submaximal exercise in either pacing mode (both 56%, P = NS). No significant changes in end-diastolic volume or stroke volume indexes occurred with exercise in either pacing mode. Our study demonstrates that in patients with normal resting LV function, AAIR and DDDR pacing are equally effective in attaining appropriate increases in cardiac output and LV filling during exercise.     

Rate Augmentation and Atrial Arrhythmias in DDDR Pacing

SPENCER, W.H., ET AL.: Rate Augmentation and Atrial Arrhythmias in DDDR Pacing. Dual chamber, rate-modulated pacemakers provide the capability of augmenting the heart rate of patients with chronotropic incompetence but also may cause atrial arrhythmias because of high rate, competitive atrial pacing. We studied ten patients with two consecutive 24-hour Holter monitors during which they were alternately programmed to either DDD or DDDR pacing in random order. Maximum heart rates (max HR) were measured at every 15-minute interval during each 24-hour period. DDDR pacing showed rate augmentation, 80 ± 7 average max HR when compared with DDD pacing, average max HR 76 ± 5. These results were even more striking when waking hours (7 am to 10 pm) were compared: average max HR 86 ± 7 DDDR versus 78 ± 4 average max HR DDD. Several patients showed marked rate augmentation. Seven of ten patients preferred DDDR pacing over DDD pacing. In the entire population, DDDR pacing did not result in an increased number of atrial arrhythmias (1.25 atrial events 124 hour) when compared to DDD pacing (1.75 atrial events/ 24 hour). We conclude that DDDR pacing provides heart rate augmentation during daily life in a clinical population while not resulting in a significant increase in atrial arrhythmias. (PACE, Vol. 13, December, Part 11, 1990)     

CHEMOTHERAPY FOR AIDS-RELATED AND ENDEMIC AFRICAN KAPOSI'S SARCOMA IN SOUTHERN AFRICA

Background. Kaposi's sarcoma (KS), either in its endemic (African) form or its AIDS-related variant, is a common neoplastic disorder seen in Southern Africa. Chemotherapy has been proven to be very effective in advanced or relapsed African Kaposi's sarcoma, but much less so in AIDS-related, endemic KS. Patients and Methods. The study consists of a retrospective analysis of the results of chemotherapy alone in 17 patients with African KS (AKS) and in 32 patients with epidemic AIDS-related KS (EKS), treated at the Johannesburg General Hospital between 1982 and 1992. Single agents included vinblastine, actinomycin D, bleomycin, and vincristine; combined regimens were largely doxorubicin/vincristine/ bleomycin or etoposide/methotrexate. Outcome classifications were: complete remission (CR), partial remission (PR), and treatment failure (TF). Results. Four of the 17 patients with AKS had CR, 10 a PR, and three were TF and died rapidly from their disease. The combined chemotherapeutic regimens produced marked symptomatic relief and even long-term remission in AKS. In patients with EKS, the response rate to chemotherapy was very low and of brief duration. No patient had a CR and debilitating side effects were common. Conclusions. The African type of AKS is a chemo-sensitive tumor, whereas the endemic type EKS, like its Western counterpart, has a dismal prognosis.     

Sclerosing haemangiomas of the lung

A series of 29 pulmonary sclerosing haemangiomas is analysed. Included is one case with multiple tumours and another with metastatic growth in a hilar lymph node. Histochemical and electron microscopic studies show that type 2 pneumocytes are an important constituent cell type though bronchial structures, tumorlets and angiomas also occur within these tumours. They are considered to be pulmonary hamartomas formed from distal lung structures. They are of slow growth and have been confused in the past with pulmonary histiocytomas and plasma cell granulomas.     

THE EFFECTS OF SOME ANTIDEPRESSANTS ON THE INDUCTION OF MORPHINE DEPENDENCE AND THE MORPHINE WITHDRAWAL SYNDROME

The effects of both acute and chronic administration of theantidepressants mianserin, nomifensine, and (+) and (–)-oxaprotilinewere assessed on naloxone-precipitated abstinence in chronicallymorphinized rats. Chronic coadministration of the antidepressantswith morphine during the induction of dependence produced nosignificant alleviation of withdrawal. Acute administrationof nomifensine prior to precipitation of abstinence with naloxoneproduced an exacerbation of the withdrawal syndrome throughstimulation of supersensitive dopamine receptor sites. By contrast,mianserin and (+)-oxaprotiline produced an overall significantalleviation of withdrawal, whereas (–)-oxaprotiline waswithout effect. The results are discussed in relation to thepossible value of antidepressant treatment during opiate withdrawal.