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Biomedical subjects

Ole A Breithardt

Publications and source records attributed to Ole A Breithardt.

13 recordsLinked to original sources
PubMed2006

Doppler echocardiography and tissue Doppler imaging in the healthy rabbit: differences of cardiac function during awake and anaesthetised examination.

OBJECTIVE: In the past years, Doppler echocardiography has evolved into a commonly used technique. More recent sophisticated advances in imaging quality have substantially improved spatial and temporal resolution allowing the adaptation of this technique to small animal models, particularly in rabbits but even in mice. Recently, parameters obtained by Tissue Doppler Imaging (TDI) have been shown to be more independent of pre- and afterload than classic hemodynamic Doppler measurements. Exploration of animal models may require anaesthesia but there is only very little information on the effect of anaesthesia on echocardiographic parameters in rabbits. METHODS: We therefore performed Doppler-echocardiographic examinations of 20 wild-type New Zealand White rabbits in awake state and under light ketamine-xylazine anaesthesia. Special focus was put on the evaluation of global and regional left ventricular systolic and diastolic function using TDI and the myocardial performance index (Tei-index). RESULTS: Doppler-echocardiographic measurements including TDI in rabbits were feasible to assess cardiac morphology and function within a short examination time. There were some distinct changes of functional parameters during anaesthesia. Exemplary for systolic function, fractional shortening, cardiac output and systolic TDI velocity of the lateral wall decreased distinctly. Global left ventricular function measured by the Tei-index deteriorated. CONCLUSIONS: Doppler echocardiography and TDI can be performed easily, quickly and safely in the rabbit. Anaesthesia with the cardiodepressive ketamine-xylazine shows some distinct Doppler-echocardiographically measurable negative effects on cardiac function. Thus, echocardiography with less cardiodepressive anaesthetic regimes or even without anaesthesia after training of the animals should be considered as alternatives whenever possible.

Anesthesia↗
PubMed2006

A new method to investigate the response to the morphology discrimination algorithm in patients with ICD.

BACKGROUND: Inappropriate therapy for supraventricular tachyarrhythmia is still a major problem in implantable cardioverter defibrillators (ICD). The morphology discrimination algorithm compares the morphology of a tachycardia electrogram with a stored template on a beat-to-beat basis. However, algorithm responders could not yet be identified prior to the occurrence of first tachycardia episodes. We analyzed whether rapid atrial pacing and/or exercise testing can be used for identification of responders and compared the results with ICD detected tachycardia. METHODS: 22 patients (16 male, 61+/-14 years) with dual-chamber ICDs have been enrolled. Patients underwent a standardized bicycle exercise testing and an atrial pacing protocol. For both tests, morphology match scores of 8 consecutive beats were analyzed for each 10-bpm-step increment above sinus rhythm. Patients were categorized as responders, if morphology match was > or = 90% of tested heart rates. During follow-up, ICD stored episodes with morphology discrimination activated were evaluated. RESULTS: There were no significant differences between morphology match (85+/-29% vs. 84+/-27%) and linear regression slope B (-0.19+/-0.87 vs. -0.20+/-0.48) during exercise testing and atrial pacing. 16 patients (73%) were classified as responders. During follow-up (739+/-338 days) 121 sustained supraventricular (n=88) and ventricular tachycardia (n=33) were detected in 10 patients (45%). Specificity for tachycardia discrimination was 78% overall, 100% in responders and 22% in non-responders. CONCLUSION: Exercise testing and atrial pacing were equally suitable for identification of patients who seem to respond to the morphology discrimination algorithm with a high specificity for ventricular tachycardia discrimination. Thus, morphology match tests are suggested to optimize tachycardia discrimination and to reduce inadequate therapies.

Algorithms↗
PubMed2005

Cardiac resynchronization therapy: Part 1--issues before device implantation.

Cardiac resynchronization therapy (CRT) has been used extensively over the last years in the therapeutic management of patients with end-stage heart failure. Data from 4,017 patients have been published in eight large, randomized trials on CRT. Improvement in clinical end points (symptoms, exercise capacity, quality of life) and echocardiographic end points (systolic function, left ventricular size, mitral regurgitation) have been reported after CRT, with a reduction in hospitalizations for decompensated heart failure and an improvement in survival. However, individual results vary, and 20% to 30% of patients do not respond to CRT. At present, the selection criteria include severe heart failure (New York Heart Association functional class III or IV), left ventricular ejection fraction <35%, and wide QRS complex (>120 ms). Assessment of inter- and particularly intraventricular dyssynchrony as provided by echocardiography (predominantly tissue Doppler imaging techniques) may allow improved identification of potential responders to CRT. In this review a summary of the clinical and echocardiographic results of the large, randomized trials is provided, followed by an extensive overview on the currently available echocardiographic techniques for assessment of LV dyssynchrony. In addition, the value of LV scar tissue and venous anatomy for the selection of potential candidates for CRT are discussed.

Cardiac Output, Low↗
PubMed2005

Cardiac resynchronization therapy: Part 2--issues during and after device implantation and unresolved questions.

Encouraged by the clinical success of cardiac resynchronization therapy (CRT), the implantation rate has increased exponentially, although several limitations and unresolved issues of CRT have been identified. This review concerns issues that are encountered during implantation of CRT devices, including the role of electroanatomical mapping, whether CRT implantation should be accompanied by simultaneous atrioventricular nodal ablation in patients with atrial fibrillation, procedural complications, and when to consider surgical left ventricular lead positioning. Furthermore, (echocardiographic) CRT optimization and assessment of CRT benefits after implantation are highlighted. Also, controversial issues such as the potential value of CRT in patients with mild heart failure or narrow QRS complex are addressed. Finally, open questions concerning when to combine CRT with implantable cardioverter-defibrillator therapy and the cost-effectiveness of CRT are discussed.

Atrial Fibrillation↗
PubMed2005

Effects of ischemia on myocardial function during rapid left ventricular pacing.

INTRODUCTION: Coronary artery disease is often accompanied with deterioration in left ventricular function. Left ventricular pacing has been shown to improve cardiac function in chronic heart failure. However, data are limited about left ventricular pacing during acute ischemia. Therefore, we studied the effects of acute myocardial ischemia on myocardial function during left ventricular pacing. METHODS: In 8 anesthetized dogs, the left ventricle was rapidly paced (180 bpm) from a basolateral and apicoseptal site during normal perfusion and mild and severe ischemia of the left anterior descending coronary artery. Effects on myocardial function were measured at each level of ischemia before and during pacing. RESULTS: Significant differences (p < 0.05) between basolateral and apicoseptal pacing were found for segmental shortening (12.1+/-1.6 vs. 10.8+/-1.6%), and QRS duration (77.3+/-4.1 vs. 85.7+/-3.8 ms) at normal coronary perfusion. During mild ischemia, significant differences (p < 0.05) were seen for myocardial contractility dP/dt(max) (1277+/-197 vs. 1158+/-156 mm Hg/s), segmental shortening (10.3+/-1.9 vs. 8.1+/-1.7%), left ventricular end-systolic pressure (76.9+/-7.5 vs. 69.6+/-7.9 mm Hg), and QRS duration, and for myocardial contractility dP/dt(max) (1033+/-209 vs. 917+/-207 mm Hg/s) and left ventricular end-systolic pressure (69.2+/-13.5 vs. 62.2+/-15.0 mm Hg) during severe ischemia. There were no significant differences in coronary blood flow during pacing from both sites. CONCLUSIONS: During acute myocardial ischemia, depression of left ventricular function was lowest, when pacing from a left ventricular basolateral site. The effects of rapid left ventricular pacing were amplified by reduced coronary perfusion pressures. The choice of pacing site did not relevantly influence coronary blood flow.

Animals↗
PubMed2004

Echocardiographic evaluation of cardiac resynchronization therapy: ready for routine clinical use? A critical appraisal.

Cardiac resynchronization therapy (CRT) has been proposed as an alternative treatment in patients with severe, drug-refractory heart failure. The clinical results are promising, and improvement in symptoms, exercise capacity, and systolic left ventricular (LV) function have been demonstrated after CRT, accompanied by a reduction in hospitalization and a superior survival as compared with optimized medical therapy alone. However, 20% to 30% of patients do not respond to CRT. Currently, patients are selected mainly on electrocardiogram criteria (wide QRS complex, left bundle branch block configuration). In view of the 20% to 30% of nonresponders, additional selection criteria are needed. Echocardiography (and, in particular, tissue Doppler imaging) may allow further identification of potential responders to CRT, based on assessment of inter- and intraventricular dyssynchrony. In addition, echocardiography may allow optimal LV lead positioning and follow-up after CRT. In the current review, the different echocardiographic approaches to predict response to CRT are discussed. In addition, the use of echocardiography to guide LV lead positioning and follow-up after CRT are addressed.

Clinical Trials as Topic↗
PubMed2004

Current status of cardiac resynchronization therapy.

PURPOSE OF REVIEW: Cardiac resynchronization therapy with biventricular pacing has rapidly emerged as an indispensable treatment option in patients with moderate-to-advanced heart failure and left bundle branch block. New findings on the pathophysiology of cardiac resynchronization therapy and its clinical effects are reviewed. RECENT FINDINGS: Several randomized trials have evaluated the effects of cardiac resynchronization therapy on cardiac haemodynamics and clinical parameters in selected heart failure patients with left bundle branch block. The effects of cardiac resynchronization therapy on mechanical synchrony have been evaluated by different imaging modalities, such as echocardiography and radionuclide angiography. Cardiac resynchronization therapy leads to improved haemodynamics at a diminished energy cost, and improves functional mitral regurgitation. This haemodynamic improvement is associated with a significantly better quality of life, improved exercise capacity, and less frequent hospitalization. Recent preliminary data suggest a positive effect on cardiac mortality. However, approximately a third of implanted patients do not benefit from cardiac resynchronization therapy, and therefore additional criteria for the identification of mechanical dyssynchrony are needed to identify those patients who will respond before implantation. SUMMARY: Many randomized trials have confirmed the benefits of cardiac resynchronization therapy in selected heart failure patients. The successful resynchronization of the ventricular activation-contraction sequence is the major determinant of acute haemodynamic and long-term clinical improvement. The diagnostic sensitivity and specificity of the non-invasive identification of mechanical dyssynchrony may be improved by echocardiography, but further research is needed to identify the optimal strategy for patient identification.

Journal Article↗
PubMed2004

Comparison of regional myocardial blood flow and perfusion in dilated cardiomyopathy and left bundle branch block: role of wall thickening.

UNLABELLED: Heterogeneous perfusion in left bundle branch block (LBBB) has been demonstrated by (99m)Tc-methoxyisobutylisonitrile (MIBI) SPECT. Locally different contraction is also associated with LBBB. Quantitative analysis of myocardial SPECT is influenced by partial-volume effects depending on systolic wall thickening. Therefore, partial-volume effects may mimic perfusion heterogeneity in LBBB. METHODS: Fifteen patients with nonischemic dilated cardiomyopathy and LBBB underwent resting (15)O-water PET, (99m)Tc-MIBI SPECT, and gated (18)F-FDG PET for analysis of wall thickening. Myocardial blood flow corrected for rate-pressure product (corrMBF), (99m)Tc-MIBI uptake, and wall thickening were determined in 4 left ventricular wall areas. In 14 patients, M-mode echocardiographic recordings were available for comparison. RESULTS: Homogeneous distribution was found for corrMBF (1.09 +/- 0.41 to 1.19 +/- 0.31 mL x g(-1) x min(-1)). (99m)Tc-MIBI uptake and wall thickening were heterogeneous (P < 0.0001), with the lowest values septal ((99m)Tc-MIBI, 65% +/- 10%; wall thickening, 16% +/- 14%) and the highest lateral ((99m)Tc-MIBI, 84% +/- 5%; wall thickening, 55% +/- 17%). Similar relationships in systolic wall thickening were observed by M-mode echocardiography (anteroseptal, 20% +/- 11%; posterolateral, 37% +/- 18%; P < 0.001). CONCLUSION: Heterogeneity of (99m)Tc-MIBI uptake in LBBB corresponds to differences in wall thickening and does not reflect distribution of corrMBF. Supplementary analysis of wall thickening is recommended when assessing (99m)Tc-MIBI SPECT in LBBB.

Adult↗
PubMed2003

Cardiac resynchronization therapy can reverse abnormal myocardial strain distribution in patients with heart failure and left bundle branch block.

OBJECTIVES: We studied the effects of cardiac resynchronization therapy (CRT) on regional myocardial strain distribution, as determined by echocardiographic strain rate (SR) imaging. BACKGROUND: Dilated hearts with left bundle branch block (LBBB) have an abnormal redistribution of myocardial fiber strain. The effects of CRT on such abnormal strain patterns are unknown. METHODS: We studied 18 patients (12 males and 6 females; mean age 65 +/- 11 years [range 33 to 76 years]) with symptomatic systolic heart failure and LBBB. Doppler myocardial imaging studies were performed to acquire regional longitudinal systolic velocity (cm/s), systolic SR (s(-1)), and systolic strain (%) data from the basal and mid-segments of the septum and lateral wall before and after CRT. By convention, negative SR and strain values indicate longitudinal shortening. RESULTS: Before CRT, mid-septal peak SR and peak strain were lower than in the mid-lateral wall (peak SR: -0.79 +/- 0.5 [septum] vs. -1.35 +/- 0.8 [lateral wall], p < 0.05; peak strain: -7 +/- 5 [septum] vs. -11 +/- 5 [lateral wall], p < 0.05). This relationship was reversed during CRT (peak SR: -1.35 +/- 0.8 [septum] vs. -0.93 +/- 0.6 [lateral wall], p < 0.05; peak strain: -11 +/- 6 [septum] vs. -7 +/- 6 [lateral wall], p < 0.05). Cardiac resynchronization therapy reversed the septal-lateral difference in mid-segmental peak strain from -46 +/- 94 ms (LBBB) to 17 +/- 92 ms (CRT; p < 0.05). CONCLUSIONS: Left bundle branch block can lead to a significant redistribution of abnormal myocardial fiber strains. These abnormal changes in the extent and timing of septal-lateral strain relationships can be reversed by CRT. The noninvasive identification of specific abnormal but reversible strain patterns should help to improve patient selection for CRT.

Adult↗
PubMed2003

Acute effects of cardiac resynchronization therapy on functional mitral regurgitation in advanced systolic heart failure.

OBJECTIVES: We studied the acute effects of cardiac resynchronization therapy (CRT) on functional mitral regurgitation in heart failure (HF) patients with left bundle branch block (LBBB). BACKGROUND: Both an decrease [corrected] in left ventricular (LV) closing force and mitral valve tethering have been implicated as mechanisms for functional mitral regurgitation (FMR) in dilated hearts. We hypothesized that an increase in LV closing force achieved by CRT could act to reduce FMR. METHODS: Twenty-four HF patients with LBBB and FMR were studied after implantation of a biventricular CRT system. Acute changes in FMR severity between intrinsic conduction (OFF) and CRT were quantified according to the proximal isovelocity surface area method by measuring the effective regurgitant orifice area (EROA). Results were compared with the changes in estimated maximal rate of left ventricular systolic pressure rise (LV+dP/dt(max)) and transmitral pressure gradients (TMP), both measured by Doppler echocardiography. RESULTS: Cardiac resynchronization therapy was associated with a significant reduction in FMR severity. Effective regurgitant orifice area decreased from 25 +/- 19 mm(2) (OFF) to 13 +/- 8 mm(2) (CRT). The change in EROA was directly related to the increase in LV+dP/dt(max) (r = -0.83, p < 0.0001). Compared with OFF, TMP increased more rapidly during CRT, and a higher maximal TMP was observed (OFF 73 +/- 24 mm Hg vs. CRT 85 +/- 26 mm Hg, p < 0.01). CONCLUSIONS: Functional mitral regurgitation is reduced by CRT in patients with HF and LBBB. This effect is directly related to the increased closing force (LV+dP/dt(max)). The results support the hypothesis that an increase in TMP, mediated by a rise in LV+dP/dt(max) due to more coordinated LV contraction, may facilitate effective mitral valve closure.

Aged↗
PubMed2002

Echocardiographic quantification of left ventricular asynchrony predicts an acute hemodynamic benefit of cardiac resynchronization therapy.

OBJECTIVES: We sought to determine whether radial left ventricular (LV) asynchrony in patients with heart failure predicts systolic function improvement with cardiac resynchronization therapy (CRT). BACKGROUND: We quantified LV wall motion by echocardiography to correlate the effects of CRT on LV systolic function with wall motion synchrony. METHODS: Thirty-four patients underwent echocardiographic phase analysis of LV septal and lateral wall motion and hemodynamic testing before CRT. Phase relationships were measured by the difference between the lateral (Phi(L)) and septal (Phi(S)) wall motion phase angles: Phi(LS) = Phi(L) - Phi(S). The absolute value of Phi(LS) was used as an order-independent measure of synchrony: the absolute value Phi(LS) = the absolute value of Phi(L) - Phi(S). RESULTS: Three phase relationships were identified (mean +/- SD): type 1 (n = 4; peak positive LV pressure [dP/dt(max)] 692 +/- 310 mm Hg/s; Phi(LS) = 5 +/- 6 degrees, synchronous wall motion); type 2 (n = 17; dP/dt(max) 532 +/- 148 mm Hg/s; Phi(LS) = 77 +/- 33 degrees, delayed lateral wall motion); and type 3 (n = 13; dP/dt(max) 558 +/- 154 mm Hg/s; Phi(LS) = -115 +/- 33 degrees, delayed septal wall motion, triphasic). A large absolute value of Phi(LS) predicted a larger increase in dP/dt(max) with CRT (r = 0.74, p < 0.001). Sixteen patients were studied during right ventricular (RV), LV and biventricular (BV) pacing. Cardiac resynchronization therapy acutely reduced the absolute value of Phi(LS) from 104 +/- 41 degrees (OFF) to 86 +/- 45 degrees (RV; p = 0.14 vs. OFF), 71 +/- 50 degrees (LV; p = 0.001 vs. OFF) and 66 +/- 42 degrees (BV; p = 0.001 vs. OFF). A reduction in the absolute value of Phi(LS) predicted an improvement in dP/dt(max) in type 2 patients for LV (r = 0.87, p = 0.005) and BV CRT (r = 0.73, p = 0.04). CONCLUSIONS: Echocardiographic quantification of LV asynchrony identifies patients likely to have improved systolic function with CRT. Improved synchrony is directly related to improved hemodynamic systolic function in type 2 patients.

Aged↗