Impact of various compression rates on interpretation of digital coronary angiograms.

According to the ACC/ACR/NEMA/ESC-guidelines, digital techniques should be replaced by cinefilm for coronary angiography. The ad hoc group of experts recently chose CD-R (CD recordable) as transport media and the JPEG standard for image compression. To avoid a possible loss of image quality, the guidelines allow a maximal data compression of only 2:1. This, however, leads to a considerable limitation: coronary angiograms cannot be viewed in real-time directly from CD. Since the possible influence of higher compression rates on image quality of coronary angiograms had not been investigated in a controlled study, we evaluated 8 various compression rates (ranging from 5:1 to 43:1) according to a prospective, randomized and blinded protocol. Four independent observers assessed 1440 angiograms using a semiquantitative score. We found that angiograms with a compression rate of 5:1 and 6:1 did not lead to a clinically relevant deterioration of image quality, whereas 11:1 was still acceptable, but 43:1 becomes unacceptable. Since no clinically relevant loss of information at a compression rate of 6:1 was experienced in our study, a modification of the ACC/ACJ/NEMA/ESC-guidelines allowing higher compression rates should be considered.

[Comparative studies of the rate of restenosis after implantation of Palmaz-Schatz and AVE-Micro stents]. / Vergleichende Untersuchungen zur Restenoserate nach Implantation von Palmaz-Schatz- und AVE-Micro-Stents.

Late results of interventional procedures utilizing coronary stents are largely determined by the rate of restenosis. So far few data are available addressing the effect of stent design, implantation pressure and morphologic factors on this crucial variable. Therefore we analyzed the coronary angiograms obtained in 259 patients before, immediately after and at 3 to 6 months following stent implantation for obstructive coronary disease. A total of 196 AVE-Micro-Stents and 142 Palmaz-Schatz-Stents were implanted into 307 stenoses. In 126 stenoses there were implanted only Palmaz-Schatz-Stents, in 170 only AVE-Micro-Stents and in 11 stenoses there were implanted Palmaz-Schatz- as well as Micro-Stents. Restenosis was defined as an over 50% stenosis at follow up. No significant difference was detected with regard to global restenosis rate at an average of 4 months following implantation (Palmaz-Schatz 33%, Micro-Stent 27%). If results were analyzed according to implantation pressure however, there was a significantly lower restenosis rate for AVE-Micro-Stents implanted with > 10 atm (17%) as compared to < or = 10 atm (35%, p < 0.02) and as compared to Palmaz-Schatz-Stents (34%, p < 0.02), which were also implanted with high pressure over 10 atm. In addition to implantation pressure, vessel segment and morphology of stenosis proved to be important determinants of late results. In this series of patients the AVE-Micro-Stent compared favourably to the Palmaz-Schatz-Stent not only with respect to a significantly lower restenosis rate, when implanted with pressures > 10 atm, but also with regard to its superior flexibility and handling characteristics.

[Waiting times and death on the waiting list for coronary artery bypass operation. Experiences in Munich with over 1,000 patients]. / Wartezeiten und Tod auf der Warteliste für eine koronare Bypass-Operation. Erfahrungen in München an über 1000 Patienten.

Short-term and long-term results are the classical parameters for quality assurance in coronary artery bypass graft surgery (CABGS). In contrast, waiting times and the inherent risks of waiting lists are usually neglected. Although the problem of "death on the waiting list" is generally known, related publications are scarce. Therefore, in January 1994, we started a prospective study to document the waiting times and the occurrence of severe complications in our patients waiting for CABGS. Between January 1, 1994 and July 31, 1996, we catheterized 1125 patients with indication for CABGS. 968 patients had social health insurance (SOCL); 157 patients were privately insured (PRIV). The urgency of CABGS was classified as "emergent", "ery urgent" and "less urgent" according to the clinical experience of the responsible cardiologists. All emergency cases could be operated the same day. 69% of the very urgent SOCL patients had to travel beyond the Munich area to be operated, while 84% of the respective PRIV patients were operated in Munich. SOCL patients were therefore separated from their families 4.3 times more frequently then PRIV. Not so urgent SOCL cases were separated from their families 1.8 times more often than PRIV. The mean waiting time for SOCL was 39.5 +/- 39.1 days in 1994, 34.9 +/- 31.5 days in 1995 and 22.7 +/- 16 days in 1996. The corresponding values of PRIV are 19.1 +/- 16.2, 19.8 +/- 14.1 and 17.2 +/- 12.6 days. The risk of dying while waiting for CABGS was 1.3% per month (15/1125). The reduction of waiting times by the factor of two between 1994 and 1996 did not, however, influence the death on the waiting list, because all deaths occurred within 4 weeks after diagnostic catheterization. Our results show that triage practices for patients requiring CABGS are not reliable. To minimize the risk of the "death on the waiting list", CABGS must be offered within a week after diagnostic coronary angiography, even for "elective" cases.

[Cardiopulmonary risk factors in patients with sleep apnea]. / Kardiopulmonale Riskofaktoren bei Schlafapnoepatienten.

Since the interaction between disorders of the respiratory coordination and cardiovascular or cardiopulmonary regulation is still largely unknown the intention of the present investigation is to point out the coincidence of cardiac arrhythmias, such as premature ventricular capture (PVC) beats and conduction blocks, with obstructive sleep apnea (OSA). For the first time a group of more than 300 patients with suspected OSA is examined concerning risk factors and frequent diagnoses as obesity, hypertension, coronary heart disease (CHD), heart insufficiency, chronic obstructive pulmonary disease (COPD), and daytime hypoxaemia. Summarizing the results of lung function test, blood gas analysis, strain-ECG, Holter-ECG and inductive plethysmography with oxygen partial pressure measurement by ambulatory work-up the following statements can be made: PVC beats occurring markedly during sleep give hints for OSA being the underlying cause, especially if the patients are young and overweight. Hypoxaemia increasing during the apnea episodes should be considered as one possible pathogenetic mechanism. Second- and third degree conduction blocks and sinus arrest coincident very often with OSA. They suggest to be life-limiting factors the more so since they often go along with CHD or heart insufficiency. Systemic arterial hypertension and overweight have the highest prevalence in OSA, signs for heart insufficiency and daytime hypoxaemia are also significantly more frequent than in non-OSA patients. We could find no hints for direct pathogenetic coherence between CHD and OSA or between COPD and OSA, nevertheless pronounced nocturnal changes in blood gases and intrathoracic hemodynamics have important influence on the cardiopulmonary and cardiovascular system, as partly illuminated in other more pathogenetic oriented studies by the present time.