Biomedical subjects

Joachim Witte

Publications and source records attributed to Joachim Witte.

3 recordsLinked to original sources

PubMed2006

Pacemaker-induced superior vena cava syndrome: clinical evaluation of long-term follow-up.

BACKGROUND: Pacemaker-induced superior vena cava (SVC) syndrome is a rare but serious complication of permanent pacemaker implantation. Because of its rarity, little is known about the long-term prognoses of such patients. METHODS: Five patients, mean age 62 +/- 11.4 years, with pacemaker-induced SVC syndrome for more than 10 years were investigated. The clinical evaluation included: exercise testing, thrombophilia lab tests, and a chest CT. RESULTS: Two of the patients manifested complications of SVC syndrome which included thoracoabdominal subcutaneous collaterals. One of these patients simultaneously developed an increase in the pacing threshold which required the implantation of epicardial leads. Three of the five patients had normal age-adjusted VO(2) AT und VO(2) max. Four of the patients were both heterozygous for a polymorphism of PAI-1 and were homozygous for a polymorphism of t-PA. One of these patients also was heterozygous for a polymorphism of factor V and glycoprotein IIb/IIIa. The chest CTs revealed extensive and varying collateral circulation patterns in all of the patients. CONCLUSIONS: The development of pacemaker-induced SVC syndrome is the result of various predisposing factors including thrombophilia. Many patients retain normal age-adjusted cardiopulmonary capacity and demonstrate stable clinical findings on the long-term as the result of the development of extensive collateral vessel systems. The most serious complication was the combination of SVC syndrome and the simultaneous malfunctioning of one of the leads requiring implantation of a new lead.

Aged↗

PubMed2004

Tissue Doppler echocardiography and biventricular pacing in heart failure: patient selection, procedural guidance, follow-up, quantification of success.

Asynchronous myocardial contraction in heart failure is associated with poor prognosis. Resynchronization can be achieved by biventricular pacing (BVP), which leads to clinical improvement and reverse remodeling. However, there is a substantial subset of patients with wide QRS complexes in the electrocardiogram that does not improve despite BVP. QRS width does not predict benefit of BVP and only correlates weakly with echocardiographically determined myocardial asynchrony. Determination of asynchrony by Tissue Doppler echocardiography seems to be the best predictor for improvement after BVP, although no consensus on the optimal method to assess asynchrony has been achieved yet. Our own preliminary results show the usefulness of Tissue Doppler Imaging and Tissue Synchronization Imaging to document acute and sustained improvement after BVP. To date, all studies evaluating Tissue Doppler in BVP were performed retrospectively and no prospective studies with patient selection for BVP according to echocardiographic criteria of asynchrony were published yet. We believe that these new echocardiographic tools will help to prospectively select patients for BVP, help to guide implantation and to optimize device programming.

Cardiac Pacing, Artificial↗

PubMed2004

Form analysis using digital signal processing reliably discriminates far-field R waves from P waves.

The correct detection of atrial arrhythmias by pacemakers is often limited by the presence of far-field R waves (FFRWs) in the atrial electrogram. Digital signal processing (DSP) of intracardiac signals is assumed to provide improved discrimination between P waves and FFRWs when compared to current methods. For this purpose, 100 bipolar and unipolar intracardiac atrial recordings from 31 patients were collected during pacemaker replacement and used for the off-line application of a novel DSP algorithm. Digital processing of the atrial intracardiac electrogram (IEGM) signals (8 bit, 800 samples/s) included filtering and calculation of the maximum amplitude and slope of the detected events. The form parameter was calculated, being the sum of the most negative value of the amplitude and that of the slope of the detected event. The algorithm collects form parameter data of P waves and FFRWs and composes histograms of these data. A sufficiently large gap between the FFRW and P wave histograms allows discrimination of these two signals based on form parameters. Three independent observers reviewed the reliability of classification with this algorithm. Sensitivity and specificity of FFRW detection were 99.63% and 100%, respectively, and no P waves were falsely classified. It can be concluded that this novel DSP algorithm shows excellent discrimination of FFRWs under off-line conditions and justify the implementation of this algorithm in future pacemakers for real-time discrimination between P waves and FFRWs. This method prevents false mode switching and allows correct and immediate intervention pacing for atrial tachyarrhythmias.

Algorithms↗