Berit Larsson

Lessons from the first patient with an implanted pacemaker : 1958-2001

On October 8, 1958 the world’s first pacemaker implantation was performed at the Karolinska Hospital in Stockholm, Sweden. The system had been developed by the surgeon A ◦ ke Senning and the physician inventor Rune Elmqvist. The patient was a 43-year-old engineer suffering from Stokes-Adams syndrome. His name was Arne H.W. Larsson (Fig. 1). At the time Senning was in charge of the experimental laboratory at the newly inaugurated Department of Thoracic Surgery at the Karolinska Hospital in Stockholm. Elmqvist was head of the Electromedical Division at Elema Schonander in Stockholm. He had studied medicine in Lund, Sweden but had not pursued a medical practice. Rather, he had become a self-taught engineer. In 1931 he had designed the first portable optical electrocardiographic (ECG) recorder and in 1948 had introduced the well-known direct writing Mingograf ink jet recorders. When Senning and Elmqvist met in 1950 they began a close cooperation in the development and testing of fibrillators and defibrillators for use in conjunction with open heart surgery, then an experimental procedure. Senning had studied and been inspired by the experimental work of Bigelow and Callaghan1,2 in stimulation for hypothermic cardiac standstill and Zoll who used external chest wall stimulation for management of Stokes-Adams attacks.3,4 During a visit to Minneapolis in 1957, Senning observed C. Walton Lillehei during open heart surgery suture stainless steel electrodes to the ventricle to manage surgically caused atrioventricular (AV) block, after closure of a ventricular septal defect. The wires were led through the thoracic wall and connected to an external pulse generator. This method avoided the discomfort and placement problems in the postoperative patient associated with Zoll’s external pacemaker. Senning considered this to be the beginning of the era of clinical pacing.5,6 On returning to Stockholm, Senning studied Lillehei’s technique experimentally and clini-

Clinical Experience with an Automatic Threshold Tracking Algorithm Study

The automatic threshold tracking pacing system algorithm developed by St. Jude Medical, verifies ventricular capture beat by beat by recognizing the evoked response (ER) following each pacemaker stimulus. The present automatic threshold tracking function requires a bipolar ventricular lead with low polarization. The aim of this study was to evaluate a new algorithm developed to use with unipolar leads with different levels of polarization. An external pacemaker with the ability to sense intrinsic R waves and measure ER signals, as well as deliver stimulus, was used. An algorithm for detecting the true ER in a unipolar sensing configuration (tip‐case) was developed. Based on the assumption that the true evoked R wave amplitude is independent of the stimulation amplitude, the algorithm calculates and subtracts the polarization present at any pacing stimulus from the measured ER. The resulting signal is analyzed to verify capture. This study comprises 35 patients of which 26 were new implants and 9 had chronic leads. The automatic threshold‐tracking algorithm was calibrated for each patient and pacing was performed at different pulse amplitudes and pulse duration. Capture was verified for each paced beat. The recordings were stored for later comparison with the tape‐recorded intracardiac heart signals. The new algorithm correctly verified capture or loss of capture for every single analyzed beat at the different pacing outputs in every individual patient. The results from this initial study suggests that the new ER detection principle will allow automatic threshold tracking to be used not only with low polarization bipolar leads but with most leads. (PACE 2003; 26:2219–2224)

Combipolar sensing in dual chamber pacing: is there still a need for bipolar leads in the atrium?

LINDE, C., et al.: Combipolar Sensing in Dual Chamber Pacing: Is There Still a Need for Bipolar Leads in the Atrium? Bipolar leads have been shown to provide superior sensing conditions compared to unipolar leads as bipolar sensing is less susceptible to interference. However, the mechanical long‐term integrity and longevity of bipolar leads is inferior to that of unipolar leads. A prospective randomized, multicenter study was performed to investigate a new atrial detection configuration called combipolar sensing. This new sensing concept is designed for the use of conventional unipolar leads in the atrium and the ventricle. While the atrial stimulation is unipolar, atrial sensing is accomplished in a bipolar way using the ventricular lead tip as the indifferent electrode. A modified dual chamber pacemaker provided with this sensing concept was implanted in 26 patients. At predischarge and at the 1‐ and 3‐month follow‐ups no significant differences in atrial sensing thresholds and P wave amplitudes were found between the unipolar and the combipolar sensing configuration at rest or during provocation. Myopotential inhibition could be demonstrated in 22 patients during unipolar sensing at sensitivity settings as “low” as 2 mV. In contrast, during combipolar sensing it could only be demonstrated in one patient once and only at the highest atrial sensitivity of 0.5 mV. Combipolar atrial sensing is feasible under normal conditions and during provocation. Myopotential interference is negligible. Thus, combipolar sensing offers comparable atrial sensing to bipolar without the disadvantages of a bipolar lead.