Verapamil increases serum ionized calcium and serum phosphate in patients with post-surgical hypoparathyroidism

The calcium homeostasis in eight patients with postoperative hypoparathyroidism was examined before and after 2 weeks of administration of verapamil in an oral dose of 80 mg three times daily. Serum ionized calcium increased during verapamil treatment (from mean +/- SD of 1.10 +/- 0.06 to 1.24 +/- 0.38 mmol l-1; P less than 0.05), as well as total serum calcium corrected for protein (from 2.11 +/- 0.13 to 2.18 +/- 0.13 mmol l-1; P less than 0.05). During treatment with verapamil there was an increase in serum phosphate (from 1.08 +/- 0.15 to 1.19 +/- 0.20 mmol l-1 P less than or equal to 0.05) and in the urinary excretion of phosphate (P/creatinine ratio from 1.22 +/- 0.69 to 1.83 +/- 0.97; P less than or equal to 0.05). The serum 1,25-dihydroxyvitamin-D3 and serum parathyroid hormone were below the detection limits both before and after verapamil treatment. There were no significant changes either of the intestinal absorption of calcium or of the urinary calcium excretion. Serum osteocalcin was insignificantly reduced after treatment (1.60 +/- 0.70 before treatment and 1.25 +/- 0.71 micrograms l-1 after treatment). Thus in patients with post-surgical hypoparathyroidism verapamil has effects on calcium and phosphorous homeostasis. Since calcium absorption was not influenced by verapamil, it is suggested that verapamil affects bone mineral metabolism.

Longevity in Patients With High Degree Atrioventricular Block Paced in the Atrial Synchronous or the Fixed Rate Ventricular Inhibited Mode

Survival in patients paced for high degree AV block has been demonstrated to be influenced by underlying cardiac disease in particular congestive heart failure. One previous study has suggested that dual chamber pacing may improve the vital prognosis for such patients. To investigate this, 74 patients treated with rate adaptive atrial synchronous (VDD) and 74 patients treated with VVI pacemakers for high degree AV block, were retrospectively studied for a mean of 5.4 years by life-table analysis. The two groups had an equal distribution of age, sex, date of pacemaker implantation, and concomitant cardiovascular diseases. Total mortality and estimated survival did not differ between the two groups. The estimated survival in the VDD group at 1, 3, and 5 years for patients without and with congestive heart failure was 94%, 86% and 78%, and 92%, 83% and 72%, respectively. In the VVI group the corresponding values were 95%, 90%, and 83% for patients without congestive heart failure and 82%, 64%, and 47% for those with congestive heart failure (P = 0.008). Compared to the expected survival rate of the general Swedish population, only the VVI group with congestive heart failure, had an excess mortality (P = 0.007). Patients with high degree AV block have a fairly normal vital prognosis irrespective of pacing mode. The prognosis for patients with congestive heart failure was negatively affected by VVI pacing. Thus, for patients with congestive heart failure the choice of pacing mode is of vital importance, whereas for patients without congestive heart failure, other factors such as feeling of well-being and exercise capacity should decide the final choice of pacing mode.

Relative importance of activation sequence compared to atrioventricular synchrony in left ventricular function

This study evaluated the relative hemodynamic importance of a normal left ventricular (LV) activation sequence compared to atrioventricular (AV) synchrony with respect to systolic and diastolic function. Twelve patients with intact AV conduction and AV sequential pacemakers underwent radionuclide studies at rest and Doppler echocardiographic studies at rest and during submaximal exercise, comparing atrial demand pacing (AAI) to sequential AV sensing pacing (DDD) and ventricular demand pacing (VVI). Studies at rest were performed at a constant heart rate between pacing modes, and the exercise study was performed at a constant heart rate and work load. Cardiac output was higher during AAI than during both DDD and VVI (6.2 +/- 1 vs 5.6 +/- 1 and 5.3 +/- 1 liters/min, p less than 0.05). LV ejection fraction was likewise higher during AAI (55 +/- 12 vs 49 +/- 11 vs 51 +/- 13, p less than 0.05). VVI with or without AV synchrony was associated with a paradoxical septal motion pattern, resulting in a 25% impairment of regional septal ejection fraction. In addition, LV contraction duration was more homogenous during AAI. Peak filling rate during AAI and VVI was higher than during DDD (2.86 +/- 1 and 2.95 +/- 1 vs 2.25 +/- 1 end-diastolic volume/s; p less than 0.05). During VVI, the time to peak filling was significantly shorter than during both AAI and DDD (165 +/- 34 vs 239 +/- 99 and 224 +/- 99 ms; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Unnecessary deaths from valvular aortic stenosis

The annual mortality from aortic valvular stenosis was calculated among potential candidates for surgical replacement of the aortic valve. From the Swedish Central Register of Causes of Death, 70 patients below the age of 80 years who had died from aortic stenosis during a 1-year period in the County of Stockholm (population 1.5 million), were identified. A retrospective analysis of their medical records showed that 37 individuals were suitable candidates for surgery. The presence of aortic stenosis had been verified at autopsy in 31 (84%) patients. The remaining six patients (16%) had their aortic stenosis diagnosis established by a thorough non-invasive investigation performed before death. Although typical signs and symptoms of aortic stenosis were recorded in all 37 patients, only six (16%) of them had been considered by their physicians to be suitable candidates for surgery prior to death. The deceased patients were compared with a group of 68 patients who had undergone aortic valve replacement for aortic stenosis during the same period. There were no significant differences between the two groups with regard to symptoms and clinical findings, except for a higher incidence of syncope in the operated group. It is concluded that, of 105 (68 surgically treated and 37 deceased) eligible patients with aortic stenosis, 37 individuals did not receive surgical care in time. The reason for this was probably insufficient knowledge of the curability of the disease.

Radiofrequency catheter ablation: the effect of electrode size on lesion volume in vivo

Radiofrequency current is a promising alternative to high voltage direct current defibrillator discharges for catheter ablation of arrhythmias. However, lesions produced with radiofrequency current are relatively small and use of high power is limited by the impedance rise that occurs with desiccation of tissue and coagulum formation. The effect of electrode size on radiofrequency ablation was assessed by comparing results of radiofrequency application using a standard 6 French electrode catheter (distal electrode 2 mm in length) to those using catheters modified with longer distal electrodes (3, 4, 6, 8, and 10 mm in length). Radiofrequency ablation was performed at 47 left ventricular endocardial sites in 20 anesthetized dogs. A constant power of 13.3 +/- 1.3 watts at 550 kHz was applied between the distal catheter electrode and a skin electrode until a total of 500 joules had been delivered or a rise in impedance occurred. Increasing electrode length from 2 to 4 mm more than doubled lesion volume from a mean of 143 to 326 mm3 (P = 0.025). Increasing electrode length beyond 4 mm produced progressively smaller lesions (157 mm3, 155 mm3, and 67 mm3 for 6-, 8-, and 10-mm electrode lengths, respectively). Impedance rise was significantly less likely with larger electrodes and took longer to occur. Increasing the size of electrodes used for radiofrequency ablation allows application of higher power without an impedance rise. Optimizing electrode size (3 or 4 mm in this study) results in larger lesions and may improve the effectiveness of radiofrequency ablation of arrhythmias.

Verapamil increases serum alkaline phosphatase in hypertensive patients

In rats, verapamil decreases intestinal absorption of calcium, increases serum parathyroid hormone (PTH), and induces osteopenia. In this prospective study, verapamil 80-120 mg three times daily was given for 2 months to 20 patients with hypertension, and the effects on calcium homeostasis were recorded. This dose of verapamil significantly reduced supine systolic and diastolic blood pressure (+/- SD) from 158/100 +/- 9/8 mmHg to 146/89 +/- 14/8 mmHg (P = 0.001). Serum alkaline phosphatase (ALP) increased significantly from 2.77 +/- 1.06 mu kat l-1 to 3.19 +/- 1.22 mu kat l-1 (P = 0.004), and isoenzymes of ALP of skeletal origin appeared after verapamil treatment. The excretion of sodium in the urine increased (Na/creatinine ratio 8.95 +/- 6.01 before and 13.16 +/- 8.26 after verapamil; P = 0.04), while the excretion of calcium, phosphate and potassium was not changed. PTH was slightly increased at the end of verapamil treatment (1.09 +/- 0.54 vs. 0.98 +/- 0.74 microgram l-1; P = 0.07), and s-1,25(OH)2D3 was also somewhat increased (22.3 +/- 14.4 vs. 17.6 +/- 4.9 ng l-1; P = 0.26). Serum Ca was not affected by verapamil (before verapamil 2.43 +/- 0.11 mmol l-1, after verapamil 2.40 +/- 0.12 mmol l-1; P = 0.28). The increase in serum ALP demonstrates that verapamil affects bone cell metabolism in man. This effect could be secondary to the enhancement of PTH secretion.

Atrial rate-responsive pacing in sinus node disease

Patients with sinus node disease (SND) who are unable to achieve an adequate increase in heart rate during exercise are candidates for atrial rate-responsive pacing (AAI-R). We have implanted 40 AAI-R systems in SND patients with an average follow-up of 12.5 +/- 8 (range 3-30) months. All the patients received an activity-sensing pulse generator (Activitrax, Medtronic or Sensolog, Siemens-Pacesetter) with a single atrial lead. Only patients with an intraoperative AV nodal block cycle-length above 100 beats min-1 were included. During follow-up, one patient was observed to have transient asymptomatic 2:1 AV-block during sleep. No patient developed persistent AV-block or chronic atrial fibrillation. Twelve patients with persistent chronotropic incompetence were assigned for a randomized double-blind crossover study, comparing exercise treadmill capacity in AAI-R with conventional atrial inhibited pacing (AAI). During AAI-R pacing the maximum heart rate during exercise was 120 +/- 1 beats min-1 compared with 97 +/- 21 beats min-1 during AAI pacing (P less than 0.01). The average exercise time increased from 11.2 +/- 2 min during AAI-pacing to 13.4 +/- 3 min during AAI-R pacing (P less than 0.01). AAI pacing should be considered for patients with SND and chronotropic incompetence.

Atrial pacing for sick sinus syndrome

Atrial pacing is the most physiological way to pace patients with sinus node disease, as it provides both AV synchrony and a normal ventricular activation pattern. Long-term studies comparing atrial and ventricular pacing imply that atrial pacing results in fewer cardiac complications and, possibly, reduced mortality. Ventricular pacing should thus, if possible, be avoided in patients with sinus node disease. The potential risk of impending high-grade AV block during atrial pacing is low, with an annual incidence around 1% if patients are selected appropriately. Approximately 40-50% of patients with sinus node disease show signs of chronotropic incompetence during physical exercise, and are thus candidates for atrial rate responsive pacing. A preoperative evaluation of candidates for atrial pacing should include long-term Holter/telemetry, exercise test, carotid sinus stimulation, and an electrophysiological study excluding significant AV conduction disturbances.

The effect of radiofrequency catheter ablation on permanent pacemakers: an experimental study

Radiofrequency current is being investigated as an alternative to direct current shock for transcatheter ablation of cardiac arrhythmias. Permanent pacemakers are known to be susceptible to high frequency electromagnetic interference. This study was performed to examine the effects of transcatheter radiofrequency ablation on permanent pacemakers in a worst-case scenario. Nineteen pulse generators representing 16 models from seven manufacturers were acutely implanted in 12 dogs to assess their function during and after ablation. Pulse generators were implanted subcutaneously in the neck and connected to a transvenous permanent pacing lead positioned in the right ventricular apex. A 6F quadripolar electrode catheter was positioned approximately 1 cm from the tip of the permanent pacing lead. Radiofrequency current from an electrosurgical unit was applied between the distal electrode of the catheter and a large diameter skin electrode placed below the left scapula. Three additional ablation sessions were performed with the catheter situated 4-5 cm from the permanent pacing lead. Each ablation consisted of 15 W of radiofrequency power, delivered for up to 30 seconds. Twelve pulse generators were falsely inhibited during radiofrequency ablation while programmed to the VVI or DDD mode, nine of which continued to be inhibited while programmed to the VOO or DOO mode. Five pulse generators paced at abnormal rates, including three examples of one pulse generator model that displayed pacemaker runaway. Runaway was observed during eight ablations, resulting in two episodes of ventricular fibrillation. Eleven pulse generators reverted to noise mode behavior during ablation. Only three pulse generators were unaffected during ablation. No reprogramming or pacing system malfunctions were observed after cessation of radiofrequency current application or during ablations greater than 4 cm from the permanent lead.(ABSTRACT TRUNCATED AT 250 WORDS)

Catheter ablation of the atrioventricular junction with radiofrequency energy

Catheter ablation of the atrioventricular junction using direct-current defibrillator discharges requires general anesthesia and may have serious side effects. Sixteen patients with drug-refractory supraventricular tachycardia underwent catheter ablation of the atrioventricular junction using radiofrequency energy. A standard 7F quadripolar electrode catheter was positioned to record the largest unipolar His potential (580 +/- 640 microV) from the distal electrode. An electrocoagulator (Microvasive Bicap 4005) supplied continuous, unmodulated energy at 550 kHz. One to 14 applications of radiofrequency current were delivered between the distal electrode and a large-diameter chest wall electrode. Transient, mild chest discomfort was reported by seven of 16 patients. None had significant arrhythmias or blood pressure changes during radiofrequency ablation. Complete atrioventricular block was produced in nine of 16 patients and high-grade second-degree atrioventricular block was produced in one patient with radiofrequency current. Attenuated His bundle electrograms could still be recorded in the remaining six patients, four of whom underwent successful atrioventricular junctional ablation using direct-current shock during the same session. Atrioventricular block persisted in all 10 patients successfully treated with radiofrequency ablation during a mean follow-up of 4.2 months. Compared with a group of historic control subjects treated with direct-current shock ablation, the 10 patients successfully treated with radiofrequency current had significantly less creatine kinase-MB isoenzyme release (5.7 +/- 5.1 vs. 22 +/- 13 IU, p = 0.006). A junctional escape rhythm was present in all patients after radiofrequency-induced atrioventricular block. In contrast, three of 10 control patients had an idioventricular escape after direct current shock ablation, and four patients had no escape rhythm at all.(ABSTRACT TRUNCATED AT 250 WORDS)

Prevalence of a haemochromatosis among men with clinically significant bradyarrhythmias

Cardiac involvement in haemochromatosis includes development of congestive heart failure and/or cardiac arrhythmias. To elucidate the importance of this disorder among patients with severe cardiac bradyarrhythmias necessitating treatment with a permanent pacemaker, such patients were screened for evidence of iron overload. Serum ferritin was determined in 232 men treated with a permanent pacemaker. In six patients (2.6%) the serum ferritin values were twice the upper normal limit. In three of these, causes other than iron overload were found (liver cancer, myeloma and amiodarone treatment), while in three (1.3%) iron overload was suspected. All the latter three had atrioventricular block of second to third degree. In these patients percutaneous liver biopsy was performed. The specimens were examined by light and electron microscopy and the iron content was determined by atomic absorption spectrophotometry. The results of these investigations showed iron overload in the liver. The prevalence of iron overload (2.0%) among this male pacemaker-treated population with AV block II-III is significantly higher than the rates previously found in urban populations in Sweden. The present data indicate that screening for haemochromatosis is of importance among males with second and third degree atrioventricular-block of unknown etiology.

Atrial pacing and the risk for AV block: is there a time for change in attitude?

A literature survey was performed to establish the prevalence of second and third degree AV block among patients with permanent atrial pacemakers because of sinus node disease. This study reviews data from 28 different studies on atrial pacing with a median follow-up of 36 months. The collected data shows a median annual incidence of second and third degree AV block of 0.6%, range 0%-4.5% with a total prevalence of 2.1%, range 0%-11.9%. There was no significant difference in follow-up time between studies that showed a low, compared with a high incidence of AV-block. Patients with sinus node disease treated with atrial pacing have a low risk of developing clinically important conduction disturbances.

Responses to carotid sinus stimulation before and after propranolol

The response to carotid sinus stimulation was studied in nine elderly men (mean age 67) with no history of cardiac disease, dizziness, or syncope. The response to manual carotid sinus pressure (during one of two studies) was positive (an RR interval of greater than 3s) in three men. But seven men showed positive responses after intravenous propranolol (0.1 mg/kg). Similarly, the RR interval was lengthened by greater than 10 ms/mm Hg in two men during neck suction. Neck suction produced a positive result in four men after intravenous propranolol. The detection of hypersensitivity of the carotid sinus in a high proportion of apparently healthy men, especially during beta blockade, suggests that an abnormal response to carotid sinus massage may not be a reliable indicator for pacemaker treatment.

Long-term pacing in sinus node disease: effects of stimulation mode on cardiovascular morbidity and mortality

In a previous retrospective treatment-comparison study of 168 patients with sinus node disease, we found a significantly higher incidence of permanent atrial fibrillation and congestive heart failure in patients treated with ventricular (VVI) pacing compared to atrial (AAI) pacing, after an average follow-up period of 2 years. To determine whether these differences persisted and whether AAI pacing resulted in a lower mortality rate than VVI pacing during long-term follow-up, the treatment groups were restudied after an average of 4 years of pacemaker treatment. The incidence of permanent atrial fibrillation was still significantly higher (p less than 0.0005) in the VVI group than in the AAI group after the additional 2 years (VVI = 47%, an increase from 29%; AAI = 6.7%, an increase from 3.4%). Congestive heart failure occurred significantly more often in the VVI group than in the AAI group (37% vs 15%, p less than 0.005). Analysis of survival data showed a higher overall mortality rate in the VVI group (23% vs 8%, p less than 0.05). The development of high-degree atrioventricular block in the AAI group remained low (total 4.5%). Thus, in sinus node disease, the advantages of AAI over VVI pacing persist during long-term follow-up. The differences in cardiovascular morbidity between the groups tend to increase with time and appear to result in a lower mortality rate among patients treated with AAI pacing.

Sniffing of ethyl chloride--an uncommon form of abuse with serious mental and neurological symptoms

Abuse of ethyl chloride is a problem which has previously been almost unknown in Sweden. Confusion, hallucinosis, ataxia, and pronounced impairment of short-term memory--all of a transient nature--and a prolonged and uncharacteristic course of abstinence reactions are some of the symptoms that occur on sniffing of ethyl chloride. The course of events in one such case is described. The authors request that references to this article outside the professional press should not be made in such a way as to facilitate abuse.

Calcium absorption and excretion in patients treated with verapamil

1. The effect of verapamil on the intestinal absorption of calcium was studied using a single isotope technique. Serum calcium and urinary excretion of calcium in the urine were followed in nine patients during treatment with verapamil for 2 months. 2. A dose of 80-120 mg (three times daily) resulted in a significant reduction of systolic and diastolic blood pressure. 3. There was no change in the intestinal calcium absorption (alpha) expressed as the fraction of given activity absorbed per hour (alpha = 0.82 +/- 0.19 vs alpha = 0.83 +/- 0.25; +/- s.d., NS) or of the excretion of calcium in urine (Ca/creatinine ratio 0.35 +/- 0.20 vs 0.31 +/- 0.33; NS). 4. Serum calcium was not significantly different before and during treatment (2.43 mmol l-1 +/- 0.10 vs 2.47 mmol l-1 +/- 0.14; NS). 5. This study demonstrates that verapamil, at doses recommended for clinical use, does not seem to affect the intestinal absorption of calcium, the serum calcium concentration or the excretion of calcium in urine.

Reduced incidence of myopotential pacemaker inhibition by abdominal generator implantation

Myopotential inhibition during permanent pacing with unipolar leads is a well-recognized clinical problem. A study was undertaken to determine if implantation of the generator in abdominal subcutaneous tissue instead of the conventional pectoral implantation site would reduce the incidence of this inhibition. Forty patients with either an abdominal (group A, n = 20) or a pectoral (group P, n = 20) generator implantation site were subjected to a standardized protocol of muscle provocation and 24-hour ECG. Pulse generators were programmed to the lowest sensitivity level (average, 2.0 mV). Pauses exceeding the stimulation interval were analyzed. During muscle provocation 85% of the patients in group P displayed inhibition, as against 5% in group A (p less than 0.001). During 24-hour ECG, the corresponding values were 95% and 15%, respectively (p less than 0.001). We concluded that abdominal generator implantation significantly reduces the incidence of myopotential inhibition in patients with unipolar pacemaker leads.

Emergency room triage by a medical specialist

This is an investigation of the impact of an emergency room triage by a medical specialist. The study encompassed patients who came to the medical section of the emergency room of a large university hospital during a two-week study period and a control period of the same length. The result showed that 36% of the patients could be sent home after the triage, thereby reducing the number of chemical tests and ECG examinations significantly (p less than 0.001). In addition, the patient's average treatment period was shortened by a mean of 63 min. No effect of the triage on hospital use of out-patient visits to the hospital during a one year follow-up period was noted. The triage procedure was safe for, and accepted by the patients, as was demonstrated by follow-ups involving investigation of the death register and personal interviews. The study shows that triage by a specialist is an effective method for reducing hospital service utilization and shortening patient treatment time.

Atrial versus ventricular pacing in sinus node disease: a treatment comparison study

Treatment with conventional ventricular pacing does not seem to influence the natural course in patients with sinus node disease (SND). In the present study the natural course of SND was compared in patients treated with ventricular (VVI) and those treated with atrial (AAI) pacing. The study population comprised 168 patients, 89 with atrial and 79 with ventricular pacing. The two groups were comparable with respect to clinical characteristics, degree of severity of SND, and length of follow-up period (average 2 years). Development of chronic atrial fibrillation and congestive heart failure was significantly more common in patients with ventricular than in those with atrial pacing (30% vs 4%, p less than 0.001; 23% vs 7%, p less than 0.01). Second-degree atrioventricular block developed in 4% of the atrially paced patients. Thus, atrial pacing is apparently superior to ventricular pacing in patients with SND.

Valsalva-induced variations in the intracardiac signal

Variations in the intracardiac signal may substantially affect the sensing function of cardiac pacemakers. As the Valsalva maneuver causes a change in heart volume, its effect on the intracardiac signal was studied in seven patients with an adequate escape rhythm who had permanent ventricular pacemakers. During generator replacement, they were asked to perform a standardized Valsalva maneuver. An increase from the baseline amplitude ranging from 5% to 70% was noted during forced expiration against the closed glottis. There was a decrease from the baseline ranging from 15% to 50% after termination of this maneuver. Similar changes were noted for the rate of voltage change (slew rate). The magnitude of these alterations was most pronounced in patients with comparatively low intracardiac amplitudes. Because marked changes in the intracardiac signal can result from the Valsalva maneuver, it might be an important source of undersensing among patients with permanent pacemakers.

Disopyramide induced second and third degree atrioventricular block in patients with bifascicular block. An acute stress test to predict atrioventricular block progression

Syncopal attacks in patients with bifascicular block may be due to both ventricular tachyarrhythmias and intermittent atrioventricular block in addition to non-cardiac causes and lead to antiarrhythmic treatment with drugs or pacemaker or both. The acute electrophysiological effect of intravenous disopyramide 2 mg/kg body weight given over five minutes on the His-Purkinje system was assessed in 27 patients with chronic bifascicular block undergoing evaluation for permanent pacemaker treatment. The predictive value of this pharmacological stress test as regards the development of atrioventricular block during follow up was analysed. The HV interval increased (mean 43%) and the QRS duration was prolonged (mean 24%). Intrahisian or infrahisian second or third degree atrioventricular block occurred in 14 patients after disopyramide administration, requiring temporary pacing in four of them. Before the electrophysiological study 15 of the 27 patients had had at least two syncopal attacks of suspected cardiac origin but no evidence of second or third degree atrioventricular block. Second or third degree atrioventricular block was subsequently recorded in five of these 15 patients during a mean of two years follow up. The sensitivity, specificity, and predictive value of second or third degree atrioventricular block produced by disopyramide administration including subsequent atrial pacing--a positive disopyramide test--as regards later development of atrioventricular block were 80%, 90%, and 80% respectively. Intravenous administration of disopyramide to patients with bifascicular block and syncopal attacks of suspected cardiac origin may provoke atrioventricular block and asystole requiring immediate temporary pacing. Furthermore, a positive disopyramide test seems to have a significant value in predicting the later development of atrioventricular block.

Clinical and electrophysiologic course of sinus node disease: five-year follow-up study

Thirty patients with symptomatic sinus node disease (SND) who 5 years previously had undergone a clinical investigation including intracardiac electrophysiologic studies with pharmacologic inhibition of autonomic tone were followed up with respect to development of arrhythmias and cardiac conduction abnormalities. In 17 of these patients a reinvestigation, including a second intracardiac study, was performed. Stable atrial fibrillation developed in five patients, paroxysmal supraventricular tachycardia occurred in one patient, and complete heart block appeared in another patient. Paroxysmal atrial arrhythmias and radiographic atrial enlargement were more common at the initial investigation in patients who during follow-up developed either stable atrial fibrillation or paroxysmal supraventricular tachycardia. Development of complete heart block was associated with signs of severe conduction defects at the initial study. General progression of conduction dysfunction as evaluated by intracardiac techniques was not a finding in this study. Conduction abnormalities limited to the atrioventricular (AV) node did not in this context predict a clinically important progression. The results indicate that those patients with SND who are predisposed to develop high-grade AV block and atrial arrhythmias can be identified by Holter monitoring, chest x-ray examination, and an intracardiac electrophysiologic study. These possibilities improve the selection of patients suitable for pacing modes preserving atrial transport.

Pacemaker dependence in patients with bifascicular block during acute anterior myocardial infarction

Eleven patients with bifascicular block complicating anteroseptal acute myocardial infarction were studied to determine the effect of prophylactic permanent pacing; eight of them also had transient high grade atrioventricular block during the acute phase of the infarction. One month after the infarction an electrophysiological study was performed and a bradycardia indicating pacemaker implanted. All the patients were followed for two years. Six had bradycardia detected, two of whom did not have high grade atrioventricular block during the index infarction. Seven patients died, four of them suddenly. There was no correlation between the electrophysiological findings and subsequent development of bradycardia. Thus pacemaker dependence seems to be common in patients with bifascicular block complicating acute myocardial infarction. Mortality is, however, also high in patients treated with pacemakers. Prospective studies to determine the predictive factors in those patients with an anterior acute myocardial infarction and who benefit from a combination of permanent pacemaker treatment and antiarrhythmic treatment are needed.

Rate hysteresis pacing: how valuable is it? A comparison of the stimulation rates of 70 and 50 beats per minute and rate hysteresis in patients with sinus node disease

The main disadvantages of VVI pacing are absence of acceleration of the heart rate and loss of atrial synchronization. The alternatives to AAI and DDD pacing are stimulation at a low rate or hysteresis in order to decrease pacing time and thus reduce AV asynchrony. Nine patients who suffered from sinus node disease and who had been given a multiprogrammable pacemaker were monitored at each of three stimulation rates: 70, 50, and 70 bpm with an inhibition rate of 50 bpm (hysteresis). The total pacing time was shortest (p less than 0.05) for the stimulation rate of 50 bpm as compared to 70 bpm and hysteresis. It was also shorter for the hysteresis mode than for the 70 bpm mode (p less than 0.05). Only for hysteresis pacing was there a significant reduction in the number of changes from conducted cardiac rhythm to pacemaker-induced rhythm. Most patients found the 50 bpm mode preferable. None favored the hysteresis mode. In patients with sinus node disease and intermittent bradycardia being permanently paced, the periods of AV-conducted rhythm may be lengthened by reducing the stimulation rate from 70 bpm, with or without hysteresis pacing, to 50 bpm. In paced patients with sinus node disease and symptoms due to AV asynchrony, it might be worth trying a decrease in the stimulation rate before resorting to other pacemaker systems.

Pacemaker dependence in transient high-grade atrioventricular block

In a prospective study 16 patients who had been given a pacemaker because of symptomatic high-grade atrioventricular block and whose conduction had been recovered were checked for their dependence on the pacemaker. During a follow-up time ranging from 32 to 158 months (median 62 months) six patients proved to be dependent on the device owing to the development of recurrent stable high-grade atrioventricular block. The subsequent return of atrioventricular block was evidently not associated with etiology, age, sex, ECG-pattern or length of follow-up period. Five additional patients equipped with a bradycardia-indicating pacemaker all proved to be pacemaker-dependent after a follow-up time ranging from 1-20 months (median 7 months), even though atrioventricular conduction had recovered and its presence had been confirmed at regular outpatient checks. It is thus evident that the conventional clinical methods are of limited value for examining the course of conduction defect and assessing the prognosis for patients whose spontaneous cardiac activity has returned after periods of symptomatic high-grade atrioventricular block. When a bradycardia-indicating pacemaker was furnished, pacemaker dependence was demonstrated in most of the patients whose atrioventricular conduction had recovered. This confirms that pacing introduced because of symptomatic high-grade atrioventricular block should not be discontinued even if a conducted heart rhythm has been established and maintained for long periods.

Clinical experience with a bradycardia indicating pacemaker

The beneficial effect of permanent pacing is controversial in certain patient groups. Once pacing has been instituted it is seldom terminated and an evaluation of pacemaker dependence is therefore not possible. An implantable pulse generator, detecting bradycardia below 30 bpm has been developed in order to broaden our knowledge about the natural history of bradyarrhythmias treated by permanent pacing. This pacemaker has been implanted in 38 patients who did not have clear-cut indications for permanent pacing. They have been followed for a mean of 13 months. Bradycardia was detected in 33 patients 1 to 21 months (4.6 mean) after implantation. Twenty-one patients did not have a detected bradycardia for long periods (months-years). Minor symptoms of lightheadedness attributable to bradycardia were reported by 15 patients during periods when the pacemaker had been activated. Holter monitoring for at least 24 hours was carried out in all patients and electronic analysis of explanted generators was performed in eleven cases. No technical failure related to the bradycardia-detecting facility was observed. The combination of diagnostic and therapeutic properties in the bradycardia-indicating pacemaker provides means for safe evaluation of pacemaker dependency over long time periods in patient groups with controversial indications for permanent pacing.

Familial cardiomyopathy--a 15-year follow-up

In 1961--1962 five families including 53 members with a familial form of cardiomyopathy (CMP) were examined. Fifteen years later a reinvestigation of the previously examined families was carried out using community registers; mortality as well as new family members were registered. Another 50 family members were thereby added. Three out of 6 young subjects who were diagnosed as having definite (2) or suspected (1) CMP at the initial examination died during the follow-up period. Four of the five families, totalling 39/41 members, were given a thorough noninvasive clinical examination including ECG, phonocardiogram exercise test, measurement of systolic time intervals and carotid arterial pulse curves, and echocardiography (Echo). A high number (17/39) of suspected or definite pathologic echocardiographic changes consistent with CMP was observed on reinvestigation. Eleven of these 17 were asymptomatic. Except for Echo, the non-invasive methods used in this study did not contribute to the diagnosis of CMP, but the non-Echo methods confirmed the Echo findings in those patients with symptoms of cardiac disease. The four reexamined families revealed a very heterogenous pattern of CMP, with both symmetric and asymmetric hypertrophy (ratio symmetric/asymmetric = 15 : 2). It may be questioned whether asymptomatic subjects with borderline changes, indicative of symmetric hypertrophy, will develop definite symmetric CMP or whether their symptoms constitute an early stage of asymmetric CMP. Echocardiographic findings may well fit with the theory of a dominant mode of inheritance.

Heart rhythm during permanent cardiac pacing

Heart rhythm was analysed with regard to spontaneous or pacemaker-induced heart activity, in a consecutive series of 282 patients paced for at least 1 year. The mean duration of pacing was 59 (13 to 180) months. The mean age of the patients was 76 (39 to 93) years. Spontaneous heart activity at all routine examinations was found in 33 (12%) of the patients. Pacemaker-induced rhythm only was recorded in 42 per cent of the patients whereas the remaining 46 per cent had varying electrocardiographic patterns. Of the patients with spontaneous rhythm at each visit, 10 had had complete heart block before pacing. Regular sinus activity was recorded at every routine examination in 74 per cent of the patients paced for reasons other than the sick sinus syndrome. This indicated that a substantial number of paced patients might be candidates for atrial triggered pacing. Patients treated with digitalis more often had asystole at the time of replacement of the pacemaker (32%) than those not so treated (19). This suggests an increased risk of sudden death in paced patients on digitalis if the pacemaker fails.