Quality assurance in prevention.

The successful prevention of caries in Sweden, as in many other countries, is an example of what might he obtained when a systematic and complete program is adopted. Fluoride programs, mechanical cleaning of the teeth, and improved nutrition and eating habits have been the most important fundamentals for the positive results. A diminished use of tobacco, with a reduced frequency of periodontitis as one of the consequences, has been successful in some groups in the population but less so in others. There is, however, evidence now in Sweden of a less active preventive approach concerning caries prophylaxis among some parents today than a generation ago. Thus, there are obvious reasons to continue with oral preventive programs, preferably integrated with general health programs. For acceptable quality in preventive programs to be obtained, concrete goals must be formulated. These should be based upon scientific findings. Those in the society who should be given priority in the program must be identified by epidemiological studies. Systems for follow-up of the preventive measures should be integrated into the programs when they are initiated. Total quality assurance programs should include parameters which describe the resources and the process needed to obtain the formulated goals. The qualifications of those involved in the process are among the most important resources for success.

Atrioventricular block progression in patients with bifascicular block assessed by repeated electrocardiography and a bradycardia-detecting pacemaker.

Syncope may be due to intermittent high-degree atrioventricular (AV) block, but a cause-relation is sometimes difficult to prove. Diagnostic methods with high predictive value proven by instruments for safe and sensitive follow-up are needed. A bradycardia-detecting pacemaker was used in patients with bifascicular block, who had been the subjects of pharmacologic stress testing of the His-Purkinje system. Thirty-seven patients were included, of whom 26 had experienced at least 1 syncopal episode of suspected bradycardia origin, and 11 had previously documented transient high-degree AV block. The electrophysiologic study included injection of disopyramide 2 mg/kg (up to 150 mg) over 5 minutes. A positive test result was defined as spontaneous or pacing-induced His-Purkinje high-degree AV block after drug or a drug-induced HV prolongation of > or = 50%. Patients were followed an average 63 months with repeated electrocardiography and a diagnostic pacemaker (n = 23). Altogether, 24 patients had a significant bradycardia diagnosed by either or both methods. The sensitivity and positive predictive values were: HV interval > or = 70 ms at baseline, 47% and 88%; a positive disopyramide test result, 75% and 80%; and HV interval > or = 70 ms or a positive disopyramide test result, 93% and 74%, respectively. Thus, the diagnostic pacemaker is a safe and sensitive tool for evaluating the information obtained at electrophysiologic study, and pharmacologic stress testing with disopyramide has an informative value in patients with bifascicular block and syncope when results at baseline are inconclusive.

Choosing the stimulation rate in patients with intermittent bradycardia and a single lead pacemaker.

In order to assess the prevalence of intermittent bradycardia in a pacemaker population, we retrospectively evaluated the occurrence of intrinsic heart activity in 229 patients with ventricular pacing. Spontaneous heart activity was recorded in 60% of the patients. However, the stimulation rate had been decreased in only 40% of the patients in order to allow for longer periods of intrinsic heart activity. In the second part of the study we prospectively assessed differences in pacemaker utilization in 19 patients with intermittent bradycardia and single lead pacemakers. All patients were observed over four periods of 14 days, with the following pacing modes: 70 beats/min, 50 beats/min, hysteresis sensing 50 beats/min, and pacing 70 beats/min; and search hysteresis sensing 50 beats/min and pacing 70 beats/min. Search hysteresis pacing is a new feature that theoretically allows for a shorter time of pacing than that of hysteresis pacing. A reduction in the stimulation rate from 70 beats/min to 50 beats/min resulted in a 60% reduction in pacemaker utilization (P < 0.05). Search hysteresis decreased pacemaker utilization by 33% (P < 0.05). There was no statistical difference between conventional hysteresis and fixed rate pacing at 70 beats/min. Most patients found fixed rate pacing preferable to hysteresis pacing. In order to minimize battery consumption and to avoid unfavorable hemodynamics in patients with ventricular pacing, the stimulation mode and rate should be optimized in patients with intermittent bradycardia to allow for longer periods of intrinsic heart activity.

Cardiac pacing and aviation.

Certain applicants with stable disturbances of rhythm or conduction requiring cardiac pacing, in whom no other disqualifying condition is present, may be considered fit for medical certification restricted to multi-crew operations. The reliability of modern pacing systems appears adequate to permit restricted certification even in pacemaker dependent subjects except for certain models of pacemakers and leads known to be at increased risk of failure. These are to be avoided. There is little evidence to suggest that newer devices are any more reliable than their predecessors. Single and dual chamber systems appear to have similar reliability up to 4 years, after which time significant attrition of dual chamber devices occurs, principally due to battery depletion. All devices require increased scrutiny as they approach their end of life as predicted from longevity data and pacing characteristics. Unipolar and bipolar leads are of similar reliability, apart from a number of specific bipolar polyurethane leads which have been identified. Atrial leads, particularly those without active fixation, are less secure than ventricular leads and applicants who are dependent on atrial sensing or pacing should be denied certification. Bipolar leads are to be preferred due to the lower risk of myopotential and exogenous EMI. Sensor-driven adaptive-rate pacing systems using active sensors may have reduced longevity and require close scrutiny. Activity-sensing devices using piezoelectric crystal sensors may be subject to significant rate rises in rotary wing aircraft. The impracticality of restricted certification in helicopters will, in any event, preclude certification. Such devices would best be avoided in hovercraft (air cushioned vehicle) pilots. Only minor rate rises are likely in fixed-wing aircraft which are unlikely to be of significance. Anti-tachycardia devices and implanted defibrillators are inconsistent with any form of certification to fly.

Carbamazepine induced bradycardia--a problem in general or only in susceptible patients? A 24-h long-term electrocardiogram study.

Carbamazepine is a first line drug in the treatment of epilepsy and trigeminal neuralgia, but may exert negative chronotropic and dromotropic effects on the cardiac conduction system. Bradyarrhythmias of different types and severity have been described, especially in the elderly, but the prevalence of arrhythmias in a larger group of carbamazepine treated patients is unknown. Forty-eight patients, 40 years of older, on continuous carbamazepine treatment because of various neurologic disorders were investigated by interview, physical examination, 12-lead surface electrocardiogram, and 24-h long-term electrocardiogram recording. The prevalence of bradyarrhythmias was compared with that in an age-stratified reference group. There was no differences between the two groups, either in the number or the duration of pauses or in the type of pauses. In conclusion, carbamazepine does not increase the risk of bradyarrhythmias in the vast majority of patients.

Evidence of increased platelet activation after thrombolysis in patients with acute myocardial infarction.

OBJECTIVE: To assess platelet activation after thrombolysis in patients with acute myocardial infarction. DESIGN: Platelet function was assessed by measurement of the in vivo synthesis of thromboxane by gas chromatography-mass spectrometry of thromboxane's major urinary metabolite, 2,3-dinor-thromboxane-B2. SETTING: Coronary care unit of Huddinge University Hospital. SUBJECTS: 30 patients with acute myocardial infarction given either streptokinase 1.5 million units intravenously over one hour + 500 mg aspirin (n = 10), 500 mg aspirin (n = 10), or neither thrombolysis nor aspirin (n = 10). RESULTS: Patients treated by thrombolysis had a 20-fold increase in thromboxane formation during thrombolysis compared with control patients not treated by thrombolysis (p = 0.0001). Until two days after thrombolysis thromboxane production in patients treated with streptokinase did not decrease to a value comparable with patients treated with aspirin but not given thrombolysis. CONCLUSION: Thromboxane production increased considerably during thrombolysis, possibly reflecting greatly enhanced platelet activation. The slow decrease in thromboxane formation after treatment with aspirin suggests that the efficacy of thrombolysis might be improved by more efficient antiplatelet treatment.

Cardiac conduction in patients with hypercalcaemia due to primary hyperparathyroidism.

OBJECTIVE: To assess whether hypercalcaemia due to primary hyperparathyroidism is associated with significant cardiac arrhythmias. DESIGN AND PARTICIPANTS: The prevalence of cardiac arrhythmias and conduction disturbances was evaluated by 12-lead ECG and 24-hour long-term ECG during pre-surgical hypercalcaemia and after post-surgical normalization of serum calcium values in 20 patients with primary hyperparathyroidism. RESULTS: After surgery, mean +/- SD calcium levels decreased from 2.85 +/- 0.1 to 2.40 +/- 0.1 mmol/l (P < 0.001). There was a significant increase in QT-intervals (0.36 +/- 0.05 vs 0.39 +/- 0.05) and QTc-intervals (0.38 +/- 0.04 vs 0.42 +/- 0.03) after surgery (P < 0.01). Long-term ECG showed no change in the minimal heart rate 47 +/- 8 vs 48 +/- 7 beats/min or in the longest RR interval 1.6 +/- 0.5 vs 1.6 +/- 0.5 s (P NS). There was no difference in the prevalence of supraventricular or ventricular arrhythmias. No episode of high-grade AV-block was observed before surgery. Circadian heart rate rhythm did not change between investigations. CONCLUSIONS: It is concluded that moderate hypercalcaemia, in spite of causing a shortening of the repolarization phase (QT-interval), has no clinically significant effect on cardiac conduction.

Risk of cancer in patients with dermatomyositis or polymyositis. A population-based study.

BACKGROUND: An association between polymyositis and cancer was first proposed in 1916, but the existence of the association has been disputed. An association between dermatomyositis and cancer is better accepted, but its magnitude is not known. METHODS: We undertook a study to provide accurate estimates of the risk of cancer in patients with dermatomyositis or polymyositis. We studied the incidence of cancer and the rate of mortality from cancer in a population-based cohort of 788 patients with dermatomyositis or polymyositis in Sweden from 1963 through 1983. The results were compared with those for the general population. RESULTS: Among the 396 patients with polymyositis, 42 cancers were diagnosed at the same time or after polymyositis was diagnosed in 37 patients (9 percent). The relative risk of cancer was 1.8 (95 percent confidence interval, 1.1 to 2.7) in the male patients and 1.7 (95 percent confidence interval, 1.0 to 2.5) in the female patients. Eighty-four males and 85 females died, and in 24 of these cases (14 percent) cancer was the principal cause of death. The mortality ratio (the rate of mortality from cancer in these patients as compared with that in the general population) was 0.90 (95 percent confidence interval, 0.6 to 1.4). Among the 392 patients with dermatomyositis, 61 cancers were diagnosed at the same time or after dermatomyositis was diagnosed in 59 patients (15 percent). The relative risk of cancer was 2.4 (95 percent confidence interval, 1.6 to 3.6) in the male patients and 3.4 (95 percent confidence interval, 2.4 to 4.7) in the female patients. Fifty-seven males and 110 females died, and in 67 of these cases (40 percent) cancer was the principal cause of death (mortality ratio, 3.8; 95 percent confidence interval, 2.9 to 4.8). CONCLUSIONS: The risk of cancer is increased in patients with polymyositis or dermatomyositis. In patients with dermatomyositis there is also a higher rate of mortality from cancer.