Delivery of inappropriate therapy of implantable cardioverter defibrillators (ICD) due to inaccurate arrhythmia detection represents a major clinical problem. Different arrhythmia detection criteria such as the "stability" of the cycle length or the suddenness of "onset" of tachycardia have been implemented in ICD software to prevent inappropriate therapy. The new Medtronic model 7223Cx ICD offers an additional detection parameter (QRS width), which reflects changes in the duration of ventricular depolarization as a tool to distinguish supraventricular from ventricular tachycardias. Although this criterion can be programmed based on ECG parameters derived from resting ECGs, this may not be sufficient since QRS width is subject to considerable changes due to transient myocardial ischemia, changes in autonomic tone, or frequency dependent effects of antiarrhythmic drugs. The present study aimed to determine frequency dependent changes in QRS width in individual patients at rest and during symptom-limited exercise testing in 16 patients with documented ventricular tachycardia (N = 13) or ventricular fibrillation (N = 3). The optimal EGM slew threshold and the individual variation of QRS width were determined. Measurements obtained at the end of the implantation procedure were compared to those performed at hospital discharge. The majority of patients showed a wider variation in QRS duration as measured from 30 consecutive cycles during exercise as compared to rest. For example, the QRS range (i.e., the difference between the maximal and the minimal QRS width measured) averaged 7 +/- 3 ms at rest and increased to 11 +/- 3 ms during exercise (P = 0.004) with an increase of > or = 4 ms observed in 11 (69%) of 16 patients. In 13 (81%) of 16 patients a reprogramming of at least one QRS width parameter from its value at the time of implantation was necessary. Thus, the QRS width measured from the intracardiac EGM shows significant intraindividual variations in different physiological conditions. For optimal programming of the QRS width parameter, measurements obtained during exercise are important.

SCHERER, M., et al.: Extension of Generator Longevity by Use of High Impedance Ventricular Leads. The resistance of a pacing lead negatively correlates to current consumption. A prospective, randomized trial was conducted to evaluate the effect of a high impedance ventricular lead (CapSure Z) on generator longevity compared to a conventional lead (CapSure SP) eighty‐nine patients were included in the study (51 male, 37 female, age 70.0 ± 10.3 years). Forty‐six patients received a CapSure SP lead (5024 bipolar), and 43 patients received a CapSure Z lead (5034 bipolar) in a randomized fashion. Follow‐up data collected at 5 days, 3, 6, and 12 months postimplant included: lead impedance, pacing and sensing thresholds, impulse energy, and estimated time to replacement. All parameters were collected via pacemaker telemetry; the time to replacement was calculated automatically by a programmed algorithm of the pacemaker. There was no difference in the performance of the atrial lead when a dual chamber device was indicated. The CapSure Z leads displayed statistically significant higher impedance values than the CapSure SP lead in all follow‐up periods. There was no significant difference in lead related complications. No significant differences were observed between pacing and sensing thresholds in both groups. The CapSure Z leads provided a significant reduction in current drain, resulting in a reduction of mean energy consumption at the 12‐month follow‐up from 10.4 ± 5.0 μJ in the CapSure SP group to 6.6 ± 1.4 μJ in the CapSure Z group (median from 9.9 μJ to 6.9 μJ, respectively), providing an estimated increase in mean longevity of more than 1 year from 81.1 ± 23.5 months in the CapSure SP group to 94.5 ± 13.4 months in the CapSure Z group (median: 76.5 months to 95.0 months, respectively). The use of a high resistance lead for ventricular pacing appears to result in a clinically relevant extension of generator longevity.

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Between 1974 and July 1989 110 operations for thoracic aortic aneurysms in 107 patients (69 males, 38 females) were performed, whose ages ranged from 14 to 74. 37 patients had an aortic valvular disease, 15 had Marfan's syndrome, 28 of these patients had a history of thoracic trauma or of previous aortic or cardiac surgery (14 posttraumatic aneurysms, 9 aneurysms after cardiac surgery, 5 after repair of aortic coarctation), 29 patients had hypertension. 63 patients underwent repair of dissecting aneurysms, 47 of non-dissecting (saccular or fusiform) thoracic aortic aneurysms. 67 repairs were emergency and 43 elective. The hospital mortality for the entire series was 34.5%. The analysis of multiple preoperative and intraoperative variables showed that mortality following thoracic aortic aneurysm repair is higher with increasing age (65.7% mortality for operations between the 60th and 70th year of age, 100% mortality beyond the 70th year of age) and emergency surgery (hospital mortality 52.2% compared with 6.9% for elective operations). A significant increase in mortality was noted related to the aneurysm type (poorer prognosis in DeBakey type I and II), to history of hypertension, to preoperative shock or to perforation of the aneurysm, including haemopericardium or haemothorax.

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From Jan. 1984 to Dec. 1988 941 patients had internal mammary artery grafting alone or with vein grafts. There were 1705 associated vein grafts and 957 internal mammary grafts, for a total of 2 662 grafts (2.8 per patient). Use of the internal mammary artery was indicated in patients younger than 70 years with a significant stenosis of the main stem or the proximal left anterior descending artery in elective operations. The overall operative mortality was 3.4%, 2.9% for men and 6.2% for women. It rose to 9.6% in patients who were in New York Heart Association Class IV. Incidence of bleeding requiring reexploration was 5.5% and an intra-aortic balloon pump was implanted in 3% because of low cardiac output. At cardiac recatheterization (on average after 12 months) 88.3% of the internal mammary grafts and 63.3% of the vein grafts were patent. In investigation of, reasons for operative mortality, measuring the free flow of the internal mammary artery showed flow rates of 32-208 ml/min only slightly depending on the blood pressure. A technique of dilatation is described that significantly increases the flow rate up to 85%. The technique has been used regularly since Nov. 1987: from that date the IMA is only used if it has a flow rate of at least 60 ml/min.