Dual Chamber Pacing with a Single-Lead DDD Pacing System

The successful application of single-lead VDD pacing during the last few years has generated the idea of single-lead DDD pacing. Preliminary data from several single-lead VDD studies attempting to pace the atrium by a floating atrial dipole are unsatisfactory, causing an unacceptably high current drain of the device. We studied the feasibility as well as the short- and long-term stability of atrioventricular sequential pacing, using a new single-pass, tined DDD lead. In eight consecutive patients (age 73+/-16 years) with symptomatic higher degree AV block and intact sinus node function, this new single-pass DDD lead was implanted in combination with a DDDR pacemaker. Correct VDD and DDD function was studied at implantation; at discharge; and at 1, 3, and 6 months of follow-up. At implant, the atrial stimulation threshold was 0.6+/-0.1 V/0.5 ms. During follow-up, the atrial pacing thresholds in different every day positions averaged 2.1+/-0.5 V at discharge, 2.9+/-0.5 V at 1 month, 3.8+/-0.4 V at 3 months, and 3.4+/-0.4 V at 6 months (pulse width always 0.5 ms). The measured P wave amplitude at implantation was 4.5+/-2.2 mV; during follow-up the telemetered atrial sensitivity thresholds averaged 2.1+/-0.3 mV. Phrenic nerve stimulation at high output pacing (5.0 V/0.5 ms) was observed in three (38%) patients at discharge and in one (13%) patient during follow-up; an intermittent unmeasurable atrial lead impedance at 3 and 6 months follow-up was documented in one (13%) patient. This study confirms the possibility of short- and long-term DDD pacing using a single-pass DDD lead. Since atrial stimulation thresholds are still relatively high compared to conventional dual-lead DDD pacing, further improvements of the atrial electrodes are desirable, enabling lower pacing thresholds and optimizing energy requirements as well as minimizing the potential disadvantage of phrenic nerve stimulation.     

Infected Endocardial Pacemaker Electrodes: Successful Open Intracardiac Removal

The long-term results after open intracardiac removal of infected pacing electrodes are presented. Methods: between 1985 and 1990 open intracardiac removal of 19 infected pacing electrodes was performed in seven patients (six male and one femalel, with a mean age of 56 years. The indications were; persisting bacteremia in three; generator pocket infection in four; endocarditis in one; and ventricular tachycardia caused by retracted electrodes in one. All electrodes were fixed in the right heart and extraction by closed methods failed. Percutaneous catheter techniques were not applied in these seven patients. In five patients two ventricular electrodes had to be removed, and in two patients a single one. A total of seven atrial electrodes were removed in six patients (one electrode each in five patients; two electrodes in one patient). All atrial and two ventricular electrodes could be removed through a pursestring suture without use of a pump oxygenator. For the removal of ten ventricular electrodes in six patients (two electrodes each in four patients; 1 electrode each in two patients) a right-sided atriotomy was necessary with cardiopulmonary bypass (CPB). Simultaneously, five new pacing systems were implanted. Results; there were no early or late mortalities. In January 1991, all seven patients are alive and in a mean New York Heart Association Class 1,3 of heart failure after a mean interval of 33 months. In all cases the infection could be controlled with a simultaneous antimicrobial chemotherapy and the postoperative period was free of major complications. Conclusion; open intracardiac removal of retained pacing electrodes with or without use of CPB is a safe procedure without major complications. It is mandatory for all infected pacing electrodes that cannot be extracted by closed methods.     

Echocardiographic Diagnosis of a Partially Thrombosed Right Coronary Artery Aneurysm in a Patient with Polycystic Disease

This report describes a patient with polycystic disease of the kidneys and the liver and an aneurysm of the proximal right coronary artery. Transthoracic and transesophageal echocardiographic imaging showed a 5 times 5 cm oval-shaped, spherical tumor in the atrioventricular corner. The tumor was partially filled with homogenous echostructures. Coronary angiography showed aneurysmatic configuration of the right coronary artery, but no region demonstrating a mass of similar size and shape as seen by echocardiography. The finding of a partially thrombosed coronary artery aneurysm was subsequently confirmed by surgery.     

Low or High Iodine Content of Contrast Medium for Cardiac Angiography?

Objective: To compare the diagnostic yield and the costs of a contrast agent with a lower iodine concentration, ioversol 300, versus the routinely used ioversol 350. Design and patients: In a prospective, randomized, double-blind study, ioversol 300 (group A patients) containing 300 mg/mL of iodine was compared with the commonly used ioversol 350 (group B patients) containing 350 mg/mL of iodine using a visual scoring system (1 = worst, 5 = best) with respect to image quality, fluoroscopy time, and amount of contrast and iodine used for coronary angiography and left ventriculography in 300 consecutive patients. The study was performed in two catheterization laboratories of different technical standards (high resolution with digital image treatment stored on Super VHS tapes in patients 1–170 and conventional 35-mm cine films in patients 171–300). Results: In group A, the quality scores for coronary angiography and left ventriculography were 4.4 (±0.7) and 4.0 (±0.8) in patients 1–170 and 3.7 (±0.8) and 4.0 (±0.8) in patients 171–300, whereas in group B the values were 4.4 (±0.6) and 4.5 (±0.6) for patients 1–170 and 3.7 (±0.8) and 4.0 (±0.8) for patients 171–300 (all NS). Fluoroscopy time (min) in group A was 9.4 (±6.1) in patients 1–170 and 11.1 (±8.8) in patients 171–300 and 11.0 (±6.6) and 10.1 (±5.7) in group B, respectively (NS). Contrast volume (mL) and iodine amount (g) in group A were 201.1 (±55.4) and 60.3 (±16.6) for patients 1–170 and 198.2 (±46.4) and 59.3 (±13.9) for patients 171–300 (NS). In group B, the corresponding numbers were 202.4 (±61.7) and 70.8 (±21.6) in patients 1–170 and 200.0 (±49.4) and 70.0 (±17.3) in patients 171–300 (P = 0.0042, patients 1–170 and P = 0.0002, patients 171–300 for iodine amount). The average cost of the contrast agent (Swiss francs) was 185.85 ± 47.9 in group A and 204.40 ± 52.4 in group B (P < 0.001). Conclusion: The use of ioversol 300 reduced the total iodine burden for cardiac catheterization with unaltered image quality and fluoroscopy time, while the costs were reduced by 9.1%.     

Epicardial, Biatrial Synchronous Pacing for Prevention of Atrial Fibrillation after Cardiac Surgery

About 30% of patients develop AF after open heart surgery. Biatrial synchronous pacing (BSP) has been shown to promote sinus rhythm in patients with paroxysmal AF refractory to drug therapy. We conducted a prospective, randomized study to test the effect of BSP via epicardial electrodes on the incidence of AF after heart surgery, as compared to conventional therapy. To apply BSP, we attached two epicardial electrodes to the right and one to the left atrium. Immediately following surgery, BSP was initiated in the AAI-Mode at a rate of 10 beats/min above the underlying rhythm (maximum 110 beats/min) and continued for 3 days, during which the rhythm was continually monitored. After 21 (age 63 +/- 9 years) of the planned 200 patients, the study was prematurely aborted because of the proarrhythmic effect of BSP: 6 of the 12 patients treated with BSP developed sensing failure (P amplitude < 1 mV), which provoked AF in 5 of these 6 patients. BSP was discontinued due to diaphragmal stimulation in two patients and due to ventricular stimulation by a dislocated left atrial electrode in one patient. Two patients in the control group (n = 9) developed AF. Using the available standard technology, BSP via epicardial electrodes is not suitable to suppress AF after heart surgery, primarily due to postoperative deterioration of atrial sensing and its profibrillatory effect. In patients requiring atrial pacing after heart surgery, sensing thresholds must be closely monitored to prevent induction of AF.     

Induction and recovery characteristics of desflurane and halothane anaesthesia in paediatric outpatients *

This study compares induction and recovery characteristics of desflurane and halothane in children undergoing elective outpatient surgery (hernia repair, circumcision and orchidopexy). Fifty-six patients one month to 12 years of age were randomly assigned to one of three study groups. In addition to nitrous oxide, group I received desflurane (D) for induction and maintenance; group II received halothane (H) for induction and desflurane for maintenance; and group III received halothane for induction and maintenance. All patients received caudal blocks at the end of surgery. There was no significant difference in induction time (mean ± SD) among the three groups (1.7 ± 0.5, 1.7 ± 0.5 and 1.0 ± 0.5 min for groups I, II and III respectively). Airway complications (coughing, breath holding, and laryngospasm) were significantly higher among the children induced with desflurane than among either of the halothane induction groups. Premedication had no effect on reducing the number of airway complications. Emergence and recovery times (mean ± SD) were significantly shorter among both desflurane maintenance groups (3.6 ± 1.7 and 11 ± 8 min) than among the group maintained on halothane (7.9 ± 3.5 and 29.9 ± 10.6 min respectively). A brief halothane induction did not compromise the fast recovery characteristics of desflurane. There was no difference among the groups in time to discharge home (approx. 3 h). This study confirms the value of desflurane as a maintenance agent in paediatric anaesthesia. In our patients, a brief halothane induction did not compromise the fast recovery characteristics of desflurane.