[Drug-induced long QT syndrome. Relevancy in intensive care medicine]. / Das medikamentös induzierte Long-QT-Syndrom. Bedeutung in der Intensivmedizin.

QT-prolonging drugs delay ventricular repolarization and, thus, favor the occurrence of Torsade de pointes (TdP). Intensive care patients are particularly endangered to suffer from this clinical picture as they often simultaneously exhibit multiple risk factors. In the following article, the most important risk factors for drug-induced long QT syndrome are described. An overview on how the QT interval can be influenced by various endo- and exogenous factors is provided. In addition, the measurement of this interval and potential sources of errors are described. Electrophysiological characteristics of TdP are delineated as well as important pathophysiological mechanisms of arrhythmogenesis, e.g., transmural dispersion of repolarization; T(peak)-T(end) interval as a marker for that dispersion is described. Potential explanations why prolongation of the QT interval is not the main or only factor for the proarrhythmic potential of QT-prolonging drugs are discussed. Furthermore, a summary of QT-prolonging drugs relevant in intensive care units is given and prevention of drug-induced long QT syndrome with consecutive TdP is discussed. Finally, recommendations for treatment of drug-induced TdP are reviewed.

Minimally invasive direct coronary artery bypass grafting: a meta-analysis.

AIM: Recently minimally invasive direct coronary artery bypass (MIDCAB) grafting has become an interesting alternative to conventional coronary artery bypass grafting, especially in patients with a high-grade left anterior descending coronary artery (LAD) stenosis unsuitable for balloon angioplasty. Although MIDCAB offers several advantages such as the avoidance of sternotomy and cardiopulmonary bypass, concerns have been raised about the technical accuracy of the anastomoses that can be performed on a beating heart. Therefore, clinical and angiographic outcomes after MIDCAB are the subject of current controversy. METHODS: A literature search for all published outcome studies of MIDCAB grafting was performed for the period from January 1995 through October 2007. Seventeen articles were enrolled in this meta-analysis. The data presented in the studies was analyzed with regard to clinical and angiographic results. RESULTS: Early and late (>30 days after MIDCAB) death rates were 1.3% (51/4081 patients) and 3.2% (130/4081 patients), respectively. The infarct rate was 0.8% (32/4081 patients; non-fatal myocardial infarction). Other minor or major complications (e.g. reoperation for management of bleeding, chest wound problems, arrhythmias, cerebrovascular accident, pericardial effusion, pulmonary complications) were reported in 781 cases. The conversion rate to sternotomy/cardiopulmonary bypass was 1.8% (74/4081 patients). A re-intervention due to graft failure was necessary in 134/4081 patients (3.3%). A total of 2556 grafts were studied angiographically immediately after surgery. One hundred and six grafts (4.2%) were occluded and 169 grafts (6.6 %) had a significant stenosis (50-99%). At 6-month follow-up, 445 grafts were studied angiographically. Sixteen grafts (3.6%) were occluded and 32 grafts (7.2%) had a significant stenosis. CONCLUSION: Clinical outcomes and immediate graft patency after MIDCAB are acceptable. However, long-term follow-up results and further randomized prospective clinical trials comparing this new technique with standard revascularization procedures in large patient cohorts are needed.

Image quality and diagnostic accuracy of non-invasive coronary imaging with 16 detector slice spiral computed tomography with 188 ms temporal resolution.

OBJECTIVE: To evaluate image quality and clinical accuracy in detecting coronary artery lesions with a new multidetector spiral computed tomography (MDCT) generation with 16 detector slices and a temporal resolution of 188 ms. METHODS: 124 consecutive patients scheduled for invasive coronary angiography (ICA) were additionally studied by MDCT (Sensation 16 Speed 4D). MDCTs were analysed with regard to image quality and presence of coronary artery lesions. The results were compared with ICA. RESULTS: 120 of 124 scans were successful. The image quality of all remaining 120 scans was sufficient (mean (SD) heart rate 64.2 (9.8) beats/min, range 43-95). The mean calcium mass was 167 (223) mg (range 0-1038). Thirteen coronary segments were evaluated for each patient (1560 segments in total). Image quality was graded as follows: excellent, 422 (27.1%) segments; good, 540 (34.6%) segments; moderate, 277 (17.7%) segments; heavily calcified, 215 (13.8%) segments; and blurred, 106 (6.8%) segments. ICA detected 359 lesions with a diameter stenosis > 50% and MDCT detected 304 of 359 (85%). Sensitivity, specificity, and positive and negative predictive values were 85%, 98%, 91%, and 96%, respectively. The correct clinical diagnosis (presence or absence of at least one stenosis > 50%) was obtained for 110 of 120 (92%) patients. CONCLUSIONS: MDCT image quality can be further improved with 16 slices and faster gantry rotation time. These results in an unselected population underline the potential of MDCT to become a non-invasive diagnostic alternative, especially for the exclusion of coronary artery disease, in the near future.

Minimally invasive direct coronary artery bypass grafting: a systematic review.

AIM: Recently minimally invasive direct coronary artery bypass grafting (MIDCAB) has become an interesting alternative to conventional coronary artery bypass grafting, especially in patients with a high-grade left anterior descending coronary artery (LAD) stenosis unsuitable for balloon angioplasty. Although MIDCAB offers several advantages such as the avoidance of sternotomy and cardiopulmonary bypass, concerns have been raised about the technical accuracy of the anastomoses that can be performed on a beating heart. Therefore, clinical and angiographic outcomes after MIDCAB are the subject of current controversy. METHODS: A literature search for all published outcome studies of MIDCAB grafting was performed for the period from January 1995 through April 2003. Sixteen articles were enrolled in this review. The data presented in the studies was analysed with regard to clinical outcome and angiographic results. RESULTS: Early mortality ranged from 0% to 4.9% and late mortality (>30 days after MIDCAB) ranged from 0.3% to 12.6%. Infarct rates (non-fatal myocardial infarction) ranged between 0% and 3.1%. Intra- and postoperative complications (wound infections, reoperation for management of bleeding, arrhythmias, stroke, etc.) occurred in 1.6-40%. The conversion rate to sternotomy/cardiopulmonary bypass ranged between 0% and 6.2%. Reinterventions due to graft failure were necessary in up to 8.9% of patients (surgical revision or percutaneous transluminal coronary angioplasty, PTCA). Short-term and mid-term angiographic outcomes are given in Table I. CONCLUSION: Clinical outcomes and immediate graft patency after MIDCAB are acceptable. However, long-term follow-up results and further randomized prospective clinical trials comparing this new technique with standard revascularization procedures are needed.

Experience with an ICD incorporating biventricular pacing.

Biventricular pacing for cardiac resynchronization is a promising therapy for symptomatic improvement in selected patients with underlying severe congestive heart failure. ICD treatment has been shown to prolong life in patients with life threatening ventricular tachyarrhythmias, but it does not improve quality of life. This review discusses current experience with ICD's incorporating biventricular pacing.

Enhanced detection criteria in implantable cardioverter defibrillators: sensitivity and specificity of the stability algorithm at different heart rates.

The lack of specificity in the detection of ventricular tachyarrhythmias remains a major clinical problem in the therapy with ICDs. The stability criterion has been shown to be useful in discriminating ventricular tachyarrhythmias characterized by a small variation in cycle lengths from AF with rapid ventricular response presenting a higher degree of variability of RR intervals. But RR variability decreases with increasing heart rate during AF. Therefore, the aim of the study was to determine if the sensitivity and specificity of the STABILITY algorithm for spontaneous tachyarrhythmias is related to ventricular rate. Forty-two patients who had received an ICD (CPI Ventak Mini I, II, III or Ventak AV) were enrolled in the study. Two hundred ninety-eight episodes of AF with rapid ventricular response and 817 episodes of ventricular tachyarrhythmias were analyzed. Sensitivity and specificity in the detection of ventricular tachyarrhythmias were calculated at different heart rates. When a stability value of 30 ms was programmed the result was a sensitivity of 82.7% and a specificity of 91.4% in the detection of slow ventricular tachyarrhythmias (heart rate < 150 beats/min). When faster ventricular tachyarrhythmias with rates between 150 and 169 beats/min (170-189 beats/min) were analyzed, a stability value of 30 ms provided a sensitivity of 94.5% (94.7%) and a specificity of 76.5% (54.0%). For arrhythmia episodes > or = 190 beats/min, the same stability value resulted in a sensitivity of 78.2% and a specificity of 41.0%. Even when other stability values were taken into consideration, no acceptable sensitivity/specificity values could be obtained in this subgroup. RR variability decreases with increasing heart rate during AF while RR variability remains almost constant at different cycle lengths during ventricular tachyarrhythmias. Thus, acceptable performance of the STABILITY algorithm appears to be limited to ventricular rate zones < 170 beats/min.

Identification of hemodynamically significant restenosis after percutaneous transluminal coronary angioplasty in acute myocardial infarction by transesophageal dobutamine stress echocardiography and comparison with myocardial single photon emission computed tomography.

BACKGROUND: Beside thrombolysis, percutaneous transluminal coronary angioplasty (PTCA) has become a well-established treatment for acute myocardial infarction. However, restenosis occurs in approximately 15%-40% of patients. Despite a frequently occurring infarct-related regional systolic dysfunction at rest, the identification of hemodynamically relevant restenosis seems important in terms of risk stratification, adequate treatment, and possible improvement of prognosis in these patients. This study was designed to assess the role of transesophageal dobutamine stress echocardiography and myocardial scintigraphy for identification of hemodynamically significant restenosis after PTCA for acute myocardial infarction. METHODS: Multiplane transesophageal stress echocardiography (dobutamine 5, 10, 20, 30, and 40 micrograms/kg per min) studies and myocardial single photon emission computed tomography (SPECT) studies were performed in 40 patients, all of whom underwent PTCA in the setting of acute myocardial infarction > or = 4 months prior to the test. Repeated coronary angiography was performed in all study patients who showed stress-induced perfusion defects or wall-motion abnormalities, or both. RESULTS: Significant restenosis (> or = 50%) was angiographically found in 15 (37.5%) of 40 patients. Of these 15 patients, transesophageal dobutamine stress echocardiography identified restenosis in 12 (80%) and myocardial SPECT in 14 (93%), yielding diagnostic agreement in 70% of patients. Echocardiographic detection of restenosis was based mainly on a biphasic response to increasing doses of dobutamine. Sensitivity and specificity for identification of hemodynamically relevant restenosis in individual patients was 80% and 92%, respectively for dobutamine stress echocardiography versus 93% and 68% for myocardial SPECT. CONCLUSIONS: Both transesophageal dobutamine stress echocardiography and myocardial SPECT were highly sensitive in identifying significant restenosis after PTCA for acute myocardial infarction. Therefore, either test, as a single diagnostic tool or especially if performed together, are clinically valuable alternatives to coronary angiography for the detection of restenosis after PTCA for acute myocardial infarction.

[Ventricular fibrillation in intra-atrial cardioversion of atrial fibrillation]. / Kammerflimmern bei intraatrialer Kardioversion von Vorhofflimmern.

Recently intra-atrial defibrillation has become an interesting alternative to external defibrillation and drug therapy for the treatment of atrial fibrillation. Low-energy intra-atrial defibrillation can be used to restore sinus rhythm f.ex. after a failed external cardioversion or during an electrophysiologic study when the administration of antiarrhythmic drugs should be avoided. Additionally this new technique has led to the development of implantable atrial defibrillators for the treatment of selected patients suffering from chronic atrial fibrillation. Intra-atrial defibrillation seems to be a highly effective and safe method, but little experience exists concerning the outcome so far. Especially the potential risk of inducing ventricular pro-arrhythmia is subject of current controversy. We report the case of a 79-year-old patient suffering from WPW syndrome with a concealed bypass tract who was subject to an intra-atrial defibrillation during an electrophysiologic study. At the beginning of the study atrial fibrillation could be converted to sinus rhythm by a single low-energy atrial defibrillation (3 J.). After a short period of time a second intra-atrial defibrillation had to be performed in the same way because of recurrent atrial fibrillation. By this atrial shock ventricular fibrillation was induced, so that high energy external defibrillation became necessary. Analyzing the ECG a correct R-wave synchronization was found, but a rather short preceding RR interval (252 ms). In conclusion, low energy atrial defibrillation is gaining importance as a highly effective new technique to restore sinus rhythm in patients suffering from atrial fibrillation resistant to conventional therapies. Nevertheless potential risks have to be considered such as the induction of ventricular pro-arrhythmia. Therefore, a correct R-wave synchronization is obligatory and shock delivery should be withheld after short RR intervals. Future prospective randomized studies will have to show whether this new technique is really safe enough and superior to the conventional methods for restoring sinus rhythm in patients suffering from atrial fibrillation.

[Dissection of the ramus interventricularis anterior in blunt chest trauma]. / Dissektion des Ramus interventricularis anterior im Rahmen eines stumpfen Thoraxtraumas.

HISTORY AND ADMISSION FINDINGS: A 57-year-old man suffered a blunt trauma to his chest when the car he was driving collided head-on with a stationary lorry. He had worn his seat belt and the air-bag had inflated on impact. He was admitted to hospital because of severe left chest pain that started 45 min after the accident. Admission physical examination indicated stable cardiopulmonary status in a fully conscious person with no obvious physical signs, in particular no contusion or other injury to the chest or fractures. INVESTIGATIONS: ECG, echocardiography, chest radiography and routine laboratory tests on admission failed to reveal any diagnostic abnormality. But subsequent ECG and biochemical tests suggested evolution of an acute anterior wall infarction, leading to the patient's transfer to the author's hospital. DIAGNOSIS AND TREATMENT: A coronary angiogram revealed traumatic dissection of the anterior interventricular branch (AIVB) around the origin of the first diagonal branch. There was also suspicion of thrombus formation and clearly impaired left ventricular function with hypo- to akinesia of the anterior wall. Myocardial scintigraphy, positron emission tomography and stress echocardiography were performed to assess the possible need for interventional or surgical revascularization. They demonstrated functioning myocardial tissue in most of the anterior wall so that minimally invasive AIVB-bypass operation was planned. CONCLUSION: The possibility of severe injury of the heart and other organs even after primarily blunt chest trauma demands careful follow-up monitoring and, if indicated, extensive noninvasive as well as invasive diagnosis and treatment.

MRI assessment of myocardial viability: comparison with other imaging techniques.

The identification of dysfunctional but viable myocardium in patients with coronary artery disease with or without a history of myocardial infarction is of paramount clinical importance since viable myocardial areas are most likely to benefit from revascularization, whereas revascularization of scar tissue will not lead to improvement of left ventricular function. In some patients cardiac catheterization itself already provides important clues to the presence of viable myocardium based on the degree of wall motion abnormalities, post-extrasystolic improvement of wall motion, the presence of collateral vessels or persisting angina in a patient with single vessel disease. However, due to the complexity of viability assessment especially in patients with severely depressed left ventricular function and multi-vessel disease, viability tests are usually requested after the results of coronary angiography are known. Among the diagnostic armamentarium to identify viable myocardium the most established techniques are single photon emission computed tomography (SPECT), positron emission tomography (PET) if available and dobutamine stress-echocardiography. With the application of magnetic resonance imaging (MRI) in clinical cardiology an important and exciting diagnostic tool has been added for the prospective identification of viable myocardium for purposes of guiding therapeutic interventions in individual patients. This article reviews comparative studies between MRI and established imaging techniques like PET, SPECT and dobutamine-echocardiography with respect to the assessment of viable myocardium in patients with acute myocardial infarction and chronic coronary artery disease.