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Biomedical subjects

G Breithardt

Publications and source records attributed to G Breithardt.

At least 307 records · Page 17Linked to original sources
PubMed1993

Sympathetic innervation of the left ventricle is impaired in arrhythmogenic right ventricular disease.

Arrhythmogenic right ventricular disease (ARVD) is a disease of unknown origin that primarily affects the right ventricle and is characterized by ventricular tachyarrhythmias which may lead to syncope and even, though rarely, sudden cardiac death. In 25 patients with ARVD, sympathetic innervation of the left ventricle was assessed by iodine-123 metaiodobenzylguanidine single photon emission tomography (123I-MIBG SPET). In addition, thallium-201 SPET was performed. The diagnosis of ARVD was made by an electrophysiological study and right and left heart catheterization including right ventricular endomyocardial biopsy. Ischaemic heart disease was excluded by coronary angiography. A group of seven patients without any evidence of heart disease served as a control group. Twenty-two of the 25 patients showed reduced uptake of 123I-MIBG. The abnormal areas were located predominantly in posterior and posteroseptal segments of the heart. No focus of increased 123I-MIBG activity could be demonstrated. No patient had signs of left ventricular involvement on left ventricular angiography. In contrast to the results of the 123I-MIBG SPET, those of 201T1 SPET were normal in 16 patients. The remaining nine patients showed areas of slight hypoperfusion not correlated with the reduced 123I-MIBG uptake. 123I-MIBG scintigraphy allows detection of left ventricular adrenergic dysinnervation in ARVD patients without morphological or functional abnormalities of the left ventricle.

3-Iodobenzylguanidine↗
PubMed1993

Surgical experience with defibrillator implantation using nonthoracotomy leads.

Between October 10, 1989, and June 17, 1991, 109 patients with life-threatening ventricular arrhythmias received an implantable cardioverter-defibrillator at our institution. In 50 patients, nonthoracotomy lead systems consisting of a subcutaneous chest wall patch electrode near the cardiac apex and one (Cardiac Pacemakers, Inc: Endotak C) or two (Medtronic: Transvene) transvenous electrodes were tested. The mean ejection fraction was 0.44 +/- 0.15 with a range from 0.19 to 0.81. Twenty-four patients had a history of open heart operation. In 43 patients the nonthoracotomy lead system was implanted, whereas in 7 patients epicardial patch lead systems were required due to elevated defibrillation thresholds during nonthoracotomy lead testing. There was one perioperative death unrelated to the operative procedure (hydrocephalus internus). Hemorrhage from the subcutaneous patch pocket or the device pocket that required reintervention occurred in 4 patients. During a mean follow-up of 13 +/- 5 months (range, 4 to 26 months) no dislocation of an endocardial lead, insulation defect, or lead fracture has been observed. In 1 patient, the lead system had to be removed due to infection of the subcutaneous patch pocket. The cardiovascular survival rate was 98% at 12 and 18 months, and freedom from sudden cardiac death was 100% at 6 and 12 months. In conclusion, defibrillator implantation using nonthoracotomy lead systems is feasible with a success rate of 86%, and during short-term follow-up no problems related to the lead system such as dislocation, fracture, or insulation defect have occurred.

Adolescent↗
PubMed1993

Electrophysiologic variables characterizing the induction of ventricular tachycardia versus ventricular fibrillation after myocardial infarction: relation between ventricular late potentials and coupling intervals for the induction of sustained ventricular tachyarrhythmias.

OBJECTIVES: The aim of this study was to analyze the relations between the presence of ventricular conduction delay and the necessary coupling intervals for the induction of sustained ventricular tachyarrhythmias. METHODS: The electrophysiologic and signal-averaged electrocardiographic (ECG) data from 83 patients with previous myocardial infarction and inducible sustained monomorphic ventricular tachycardia (n = 71) and ventricular fibrillation (n = 12) were analyzed. RESULTS: The sum of the coupling intervals needed for inducing ventricular tachycardia and ventricular fibrillation was 485 +/- 59 ms and 387 +/- 36 ms, respectively (p < 0.001). The mean difference between the effective refractory period and the second coupling interval for the induction of ventricular tachycardia and ventricular fibrillation was -3 +/- 40 ms and 24 +/- 29 ms, respectively (p < 0.02). QRS duration and duration of terminal low amplitude signals of the QRS complex (p < 0.004) were longer in patients with inducible ventricular tachycardia than in patients with inducible ventricular fibrillation. The root mean square of the voltage during the last 40 ms of QRS complex was lower in patients with inducible ventricular tachycardia than in patients with inducible ventricular fibrillation (p < 0.007). Patients with inducible ventricular tachycardia presented with a greater prevalence of ventricular late potentials than that of patients with inducible ventricular fibrillation (p < 0.007). For arrhythmia induction, significantly shorter coupling intervals were necessary in patients without than in patients with ventricular late potentials. A positive correlation was found between the cycle length of the induced ventricular tachycardia and the filtered QRS duration as well as with the sum of the coupling intervals. CONCLUSIONS: Induction of ventricular fibrillation requires shorter coupling intervals than does induction of ventricular tachycardia. The presence of ventricular conduction delay seems to be a marker of facilitated induction of sustained monomorphic ventricular tachycardia rather than of ventricular fibrillation. The coupling intervals required to induce ventricular tachycardia or fibrillation are longer in patients with than in those without an abnormal signal-averaged ECG.

Adult↗
PubMed1993

Do patients with an implantable defibrillator live longer?

OBJECTIVES: This study was done to provide information on the potential benefit of implantable cardioverter-defibrillator therapy regarding sudden and arrhythmia-related deaths and to examine whether such therapy improves survival. BACKGROUND: Implantation of automatic cardioverter-defibrillators is reported to abort sudden cardiac death due to malignant tachyarrhythmias. METHODS: Between 1989 and 1992, 107 patients were screened for implantation of a third-generation implantable cardioverter-defibrillator combined with endocardial leads. Mean age was 57 +/- 13 years and mean ejection fraction was 40 +/- 15%. Sudden death, total arrhythmia-related death and total cardiac death were compared with the occurrence of fast ventricular tachyarrhythmias (> 240 beats/min), assuming that most of these arrhythmias would have been fatal without treatment by the implantable cardioverter-defibrillator. RESULTS: The surgical mortality rate was 2.7% in all 107 patients and 1% in the 99 patients who qualified for endocardial leads. During a follow-up period of 12 +/- 8 months, actuarial survival rate free of events at 6 months as well as at 12 and 18 months was 100% for sudden death, 97% for total arrhythmia-related death and 95% for total cardiac death. In contrast, after 6, 12 and 18 months, the rate of survival free of fast ventricular tachycardia was only 83%, 74% and 69%, respectively, and the rate of survival free of any ventricular tachyarrhythmia was only 59%, 49% and 40%, respectively. CONCLUSIONS: The outcome of patients treated with an implantable cardioverter-defibrillator and endocardial defibrillation leads is excellent. For many patients, this treatment is probably lifesaving.

Adult↗
PubMed1993

Effective pulmonary capillary pressure in experimental myocardial ischaemia.

Effective pulmonary capillary pressure and extravascular lung water were investigated in dogs (n = 9) with normal heart function and after development of acute myocardial ischaemia. During control, no impairment of cardiopulmonary performance was observed. Extravascular lung water was in the normal range (8.1 +/- 2.8 ml.kg-1) and the effective pulmonary capillary pressure accounted for 1.36 +/- 0.53 kPa (10.2 +/- 4 mmHg). No correlation between extravascular lung water and effective pulmonary capillary pressure was observed (r2 = 0.347, P = 0.06). Arterial (RPA) and venous pulmonary resistance (RPV) were 70 +/- 15% and 30 +/- 6%, respectively. Acute myocardial ischaemia was induced by one stage occlusion of the left anterior descending (LAD) coronary artery; measurements during the ischaemia phase were performed 60 min following LAD occlusion. Myocardial ischaemia resulted in moderate changes of cardiac output, heart rate and left ventricular end-diastolic pressure. Oxygenation deteriorated, but no hypoxaemia occurred in any animal and CO2 elimination remained unchanged. Extravascular lung water was elevated (16.5 +/- 7.9 ml.kg-1, P < or = 0.01), and effective pulmonary capillary pressure was higher when compared with the control state (2.32 +/- 1.05 kPa (17.4 +/- 7.9 mmHg), P < or = 0.01). There was a significant correlation between both parameters (r2 = 0.528, P < or = 0.05). Longitudinal distribution of pulmonary vascular resistance was altered, and RPA decreased to 60 +/- 13% (P < or = 0.05), while RPV increased to 40 +/- 8% (P < or = 0.05). It is concluded that development of lung oedema is related to elevated effective pulmonary capillary pressure in dogs with acute myocardial ischaemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Value of intravascular ultrasound in the diagnosis and characterization of patent ductus arteriosus in an adult patient.

We report the case of a 47-year-old patient with a patent ductus arteriosus who underwent angiography and percutaneous intravascular ultrasound examination. The case illustrates that intravascular ultrasound contributes to the characterization of patent ductus arteriosus when a surgical or trans-catheter closure is planned, as calcifications of the wall as well as aneurysmal dilatations can be ruled out. Furthermore, measurements of the diameter of the ductus can be made.

Diagnosis, Differential↗
PubMed1993

The signal-averaged ECG: time-domain analysis.

During the past decade, the high-resolution electrocardiogram as a non-invasive technique for the detection of ventricular late potentials has developed from an experimental method into a routinely applied non-invasive method for risk stratification of patients after myocardial infarction. Meanwhile, several approaches have been developed for the detection of ventricular late potentials including time-domain analysis, frequency-domain analysis and spectrotemporal mapping. Clinical applications are no longer limited to patients after myocardial infarction, but cover a wider spectrum of different cardiac diseases. This review focuses on some methodological aspects as well as on the results and current clinical applications of the analysis of the signal-averaged ECG in the time domain.

Action Potentials↗
PubMed1993

Late potentials, heart rate variability, and electrocardiography.

Low-amplitude, high frequency components in the terminal QRS-complex (so-called late potentials) are thought to arise from diseased myocardial tissue that forms the "electrophysiologic substrate" for ventricular tachyarrhythmias. Recording of late potentials is now commercially available in several systems and may possibly become clinically routine in the near future. Increased attention has been given recently to heart rate variability as an indicator of conditions of the autonomic nervous system that might trigger ventricular tachyarrhythmias. The value of late potentials and heart rate variability for identification of patients at risk for developing life-threatening ventricular tachyarrhythmias is discussed, as are the other applications and limitations of both methods.

Action Potentials↗
PubMed1993

Radiofrequency catheter ablation of ventricular tachycardia following implantation of an automatic cardioverter defibrillator.

OBJECTIVES: The present study reports on the complementary role of two nonpharmacological options of antiarrhythmic therapy. BACKGROUND: Catheter ablation, antitachycardia surgery, and the implantable cardioverter defibrillator (ICD) have become important tools in the management of ventricular tachyarrhythmias. However, the emergence of ventricular tachyarrhythmias after implantation of an ICD is possible because the arrhythmogenic substrate is not affected. PATIENTS AND METHODS: Six of 180 patients developed frequent episodes of monomorphic ventricular tachycardia (n = 2) or incessant ventricular tachycardia (n = 4) following implantation of an ICD and underwent radiofrequency (RF) catheter ablation. Catheter ablation was performed using a RF generator HAT 200. Energy was delivered between a 4-mm tip electrode of the ablation catheter and a patch electrode. RESULTS: Catheter ablation was done 6.8 +/- 5 months following ICD implantation; 6 +/- 2.2 RF impulses were delivered at the site of origin of ventricular tachycardia characterized by early endocardial activation during ventricular tachycardia, identical pace mapping and long latency between stimulus, and QRS-complex in five patients. New bundle branch reentry was the underlying mechanism of ventricular tachycardia in one patient. RF catheter ablation resulted in termination of incessant ventricular tachycardia. Immediately postablation, the documented ventricular tachycardia was rendered noninducible in all patients. No ICD malfunctions have been observed. One patient died due to heart failure 24 hours after successful ablation of the incessant ventricular tachycardia. During a follow-up of 5-19 months, episodes of ventricular tachycardia recurred in four patients. All episodes could be controlled by the ICD without frequent cardioversions. CONCLUSION: RF catheter ablation is a complementary therapeutic option in case of frequent or incessant ventricular tachycardia after ICD implantation.

Adult↗
PubMed1993

Signal averaging in patients with coronary artery disease: how helpful is it?

In patients who have survived acute myocardial infarction, the presence of ventricular late potentials using the high resolution signal-averaged ECG indicates areas of slow conduction and delayed activation that may potentially serve as a substrate for malignant ventricular arrhythmias. Although detection of late potentials is technique specific, signal-averaged analysis in the time or frequency domain may be a useful index for risk stratification with regard to ventricular tachycardia or sudden cardiac death. The sensitivity and specificity of late potentials for this purpose may be enhanced by combination with other variables, such as left ventricular ejection fraction and presence of complex ventricular ectopy. Therefore, the presence of ventricular late potentials in postmyocardial infarction patients, particularly in those patients with impaired left ventricular function, identifies those patients who are at high risk of malignant ventricular tachyarrhythmias. However, the strategies for prevention of serious arrhythmia complications during follow-up need to be established. The negative predictive value of late potentials is very high. Thus, the absence of late potentials indicates a low propensity to sustained ventricular tachycardia or sudden death, even in the presence of complex ventricular ectopy. Interventions may therefore not be necessary or should even be avoided. The incidence of late potentials in patients with spontaneous or induced ventricular fibrillation is lower and, if present, less pronounced than in those with sustained monomorphic ventricular tachycardia. This presumably is due to a lower degree of conduction delay, which serves as a substrate for reentry. Therefore, the ability of the signal-averaged ECG to predict a propensity to ventricular fibrillation is limited. Despite these limitations, the signal-averaged ECG may be used as a risk predictor in evaluation of patients after myocardial infarction. Unfortunately, at least as far as time domain analysis is concerned, it cannot be used as an efficacy predictor for response to pharmacologic interventions. Further studies will determine whether other modes of signal-averaged analysis can predict the response to drugs.

Action Potentials↗
PubMed1993

Unexpected emergence of manifest preexcitation following transcatheter ablation of concealed accessory pathways.

INTRODUCTION: The basis for anterograde or retrograde unidirectional block of accessory pathways still remains a controversial issue. METHODS AND RESULTS: Four of 19 consecutive patients (1 male, 3 female; ages 27 to 34 years) who underwent transcatheter ablation of concealed accessory pathways developed manifest preexcitation after the ablation. The location of the concealed accessory pathways in these four patients were right lateral, left posteroseptal, left posterolateral, and left lateral. Radiofrequency current was used in three of the four patients and high energy direct current in one patient. After ablation, manifest preexcitation was observed in these four patients for the first time. Manifest preexcitation developed immediately after ablation in two of the four patients and after 4 and 14 days in the other two. Detailed endocardial mapping revealed that the manifest preexcitation originated from the same location as the concealed pathways. Subsequently, catheter ablation was successfully performed in three of the four patients using radiofrequency current. One patient underwent successful surgical ablation. No recurrence of preexcitation was observed during a follow-up period of 9 to 38 months. All patients remained free of arrhythmias. CONCLUSION: The basis for this unexpected emergence of preexcitation in these patients with only retrograde conducting accessory pathways deserves further investigation. Although not compared in the present study, this phenomenon has not been reported in patients who underwent surgical interruption of accessory pathways. We postulate that a lesion at the site of insertion of the accessory pathway had modified the anterograde conduction capacity.

Adult↗
PubMed1993

Arrhythmogenic right ventricular disease: MR imaging vs angiography.

OBJECTIVE: Arrhythmogenic right ventricular disease (ARVD) is increasingly found in young adults with ventricular arrhythmias and is characterized by ventricular tachycardia originating within the right ventricle and regional or diffuse abnormalities in the contraction of the right ventricle. Until now, the gold standard for the detection of global and regional abnormalities of the right ventricular wall has been angiography combined with biopsy. The purpose of the current study was to compare MR imaging with angiography for assessing the location and extent of morphologic and functional abnormalities in patients with ARVD. SUBJECTS AND METHODS: Electrocardiographically gated spin-echo and cine gradient-echo MR imaging of the heart was performed in 36 consecutive patients with biopsy-proved ARVD. Patients were prospectively separated into two groups according to the results of invasive electrophysiologic tests (18 with inducible ventricular tachycardia during invasive electrophysiologic studies [ARVD 1] and 18 without inducible ventricular tachycardia [ARVD 2]) and compared with 11 control subjects. Global and regional morphology and function of the right ventricle were assessed with MR imaging, and those findings were compared with angiographic findings. RESULTS: Right ventricular ejection fraction was significantly lower in patients with ARVD 1 than in patients with ARVD 2 or in control subjects. Regional abnormalities of the right ventricular wall also were more pronounced in patients with ARVD 1 than in patients with ARVD 2. Signal-intensity increases corresponding to fatty replacement shown by biopsy were seen in 33% of patients with ARVD 1 and in 11% of patients with ARVD 2. Abnormal regions of the right ventricular wall seen on MR images corresponded to angiographic findings in 86% of patients. Comparison with control subjects showed that patients with ARVD 1 had a significant delay in diastolic relaxation of the right ventricle. CONCLUSION: Our results show that MR imaging can be used to assess morphologic alteration, tissue abnormalities, and global as well as regional dysfunction of the right ventricle in patients with ARVD. It may become a useful clinical tool for diagnosing and grading ARVD and a worthy substitute for angiography and biopsy in the follow-up of patients with ARVD.

Adolescent↗
PubMed1993

[Torsade de pointes].

Torsade de pointes (TDP) is a polymorphic ventricular tachycardia with a particular electrocardiographic pattern of continuously changing ("twisting") morphology of the QRS complex occurring in the setting of delayed myocardial repolarization (i.e., prolongation of the QT interval). TDP may develop in the setting of an idiopathic disorder (Jervell/Lange-Nielsen syndrome, Romano-Ward syndrome, sporadic long QT syndrome) or may be induced by pharmacologic agents which prolong the QT interval, as well as by other clinical circumstances under which repolarization is delayed (e.g., hypokalemia, hypomagnesemia, bradycardia) (acquired long QT syndrome). Since the treatment of TDP strongly differs from that of conventional ventricular tachycardia, correct diagnosis is critical as it guides the treating physician in selecting the appropriate mode of therapy. In this paper mainly the electrocardiographic criteria presently used for the correct identification of this unusual form of ventricular arrhythmia are presented. Additionally, the potential mechanisms and therapeutic modalities of TDP are discussed.

Anti-Arrhythmia Agents↗
PubMed1993

[Intravascular ultrasound in peripheral calcified vascular lesions: comparison with direct magnification radiography].

Intravascular ultrasound can detect calcified peripheral arteriosclerotic lesions by hyperdense echo patterns and shadowing of subintimal layers. Nevertheless, 20 MHz ultrasound systems have not been validated for the detection of peripheral calcifications; besides, it is unknown whether the depiction of calcified lesions by intravascular ultrasound depends on the morphology of the calcification. Histological evaluation of severely calcified arteries is difficult because the preparation of those specimens often causes artefacts, e.g., fracture of calcified structures. Direct magnification radiography, currently used in forensic medicine or skeleton examination, is based on a minimized focus and enables the edge-enhanced views of calcifications with high discrimination. In this in-vitro-study direct radiological magnification was used to validate intravascular ultrasound. Forty-nine segments of human peripheral arteries were fixed in formalin, examined with intravascular ultrasound and, as a reference, radiographically magnified using a newly developed microfocus x-ray tube. Sensitivity, specificity, positive and negative predictive value, and accuracy of intravascular ultrasound for the detection of calcified wall areas were determined and compared to the appearance (configuration, circumferential and areal expansion, density, number of fragments) of these calcifications. Thicknesses of 110 single calcified structures were estimated on sonograms and radiograms. The overall sensitivity of the 20 MHz intravascular ultrasound system for the detection of calcification in 913 sectors was 70%, specificity 53%, positive predictive value 66%, negative value 58% and accuracy 62%. The depiction of calcified regions by direct magnification radiography showed that the sensitivity strongly depended on the density of the calcification. Sensitivity was 81% with calcified lesions of high density, but only 51% with lesions of low density.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1993

[Oral anticoagulation for prevention of thromboembolism in non-rheumatic atrial fibrillation: indications, effectiveness and risk].

Oral anticoagulation in patients with rheumatic heart disease for prevention of systemic thromboembolism is accepted clinical practice. The incidence of stroke in patients with nonrheumatic atrial fibrillation is about five times the rate of patients in sinus rhythm. However, contradictory findings in several small retrospective studies have precluded determination of a gold standard for patients with nonrheumatic atrial fibrillation so far. Recently, the results of five prospective, placebo-controlled studies in patients with nonrheumatic atrial fibrillation treated with anticoagulation have been published. A consistent risk reduction of thromboembolism ranging from 37 to 87% in patients treated with warfarin was reported. This risk reduction occurred in excess of a relatively low incidence of intracerebral and/or fatal bleeding complications. The efficacy of prevention of thromboembolism was comparable for high intensity anticoagulation (International Normalized Ratio (INR) 2.8-4.2) and low dose anticoagulation (INR 1.5-2.7). However, fatal and/or intracerebral bleedings only occurred with INR > or = 2.6. In subgroup analysis, recent congestive heart failure, arterial hypertension, and previous apoplex or arterial thromboembolism were independent clinical predictors of increased risk for thromboembolism, whereas results in patients with chronic and intermittent atrial fibrillation were comparable. In 69 patients with lone atrial fibrillation, no single event occurred in the follow-up period. Thus, lone atrial fibrillation does not seem to carry an increased risk for stroke when strict criteria for diagnosis of lone atrial fibrillation are applied. In two of the five studies, aspirin was additionally randomized. Since contradictory findings resulted, the role of aspirin for prophylaxis of stroke still needs to be determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1993

[Reproducibility of the signal-averaged, high-pass filtered electrocardiogram].

In order to test the reproducibility of the signal-averaged electrocardiogram (SAECG) using Simson's method (high-pass filter cutoff frequency 25 Hz, orthogonal leads, recording of 133 s per lead), 121 patients were examined. In all patients, two signal-averaged ECGs were performed on the first day of the study immediately after each other, using identical electrode position. In a subgroup of 47 patients, the same procedure was repeated 3 days later. There was no difference between the mean values of conventionally calculated averaging parameters (heart rate, QRS-duration, root-mean-square voltage in the terminal 40 ms of the highly amplified and filtered QRS-complex [V40], the low amplitude signal duration under 40 microV in the terminal portion of the QRS-complex [LAS], total root-mean-square voltage of the QRS-complex), both with regard to immediate and short-term reproducibility. Thus, conventionally calculated averaging parameters are well reproducible.

Adolescent↗