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Biomedical subjects

M Achtelik

Publications and source records attributed to M Achtelik.

9 recordsLinked to original sources
PubMed2000

Assessment of the chronotropic response at the anaerobic threshold: an objective measure of chronotropic function.

The evaluation of the heart rate response to exercise is important for the diagnosis of chronotropic incompetence and the assessment of a rate responsive algorithm of sensor-controlled pacemakers. The aim of the present study was to examine a classification of the chronotropic response at an individually moderate exercise level. Sixteen pacemaker patients (patient group, age 62.9 +/- 7.6 years) with sick sinus syndrome and 15 age-matched healthy subjects (control group, age 57.6 +/- 9.4 years) underwent a maximum cardiopulmonary exercise test on a treadmill after a protocol with individually selected incremental steps. To analyze the patients' intrinsic heart rate response, the rate responsive mode of the pacemaker was switched off. Chronotropic incompetence was diagnosed in eight patients whose maximal heart rate was < 80% of the age-predicted heart rate. The heart rate at the anaerobic threshold was significantly lower in the chronotropically incompetent subgroup than in the chronotropically competent patients and the healthy subjects (85.9 +/- 6.6 beats/min vs 100.3 +/- 9.9 beats/min and 112.9 +/- 11.7 beats/min, respectively). The chronotropic slope of the heart rate reserve as a function of the metabolic reserve was significantly higher in the control group than in the patient groups with either mild or severe chronotropic incompetence (0.94 +/- 0.17 vs 0.64 +/- 0.08 and 0.43 +/- 0.14, respectively). Furthermore, the chronotropically incompetent response could be divided into a linear type with and without a threshold, an exponential, and a logarithmic type. The anaerobic threshold was an objectively detectable breakpoint at an individually moderate exercise level that could be used for characterization of chronotropic function. At the anaerobic threshold, a physiological heart rate response was about 220--age--50 beats/min. A deviation of more than 10 beats/min below this physiological value characterized chronotropic incompetence.

Algorithms↗
PubMed2000

Impact of biventricular pacing on mortality in a randomized crossover study of patients with heart failure and ventricular arrhythmias.

Biventricular (BV) pacing is under clinical investigation for the treatment of heart failure. Its impact on mortality is unknown. Patients with heart failure and ventricular tachyarrhythmias received an implantable cardioverter defibrillator with BV pacing capability. Patients were randomized 1:1 to BV pacing or no pacing, then crossed over to the alternate mode after 3 months. All-cause mortality was measured in each arm up to the point of crossover. Fifteen of 222 patients died between implant and crossover. Five patients died while programmed to BV pacing and 19 died while programmed to no pacing. Survival in the BV pacing arm was 93 +/- 4% versus 86 +/- 6% in the no pacing arm (P = 0.18). In a patient population with symptomatic heart failure and ventricular arrhythmias, BV pacing does not appear to be associated with excess mortality. Larger and longer studies will be needed to determine if BV pacing confers a survival benefit.

Aged↗
PubMed2000

Performance of a new steroid-eluting coronary sinus lead designed for left ventricular pacing.

The Ventak CHF/CONTAK CD Biventricular Pacing Study is a prospective randomized trial to examine the safety and efficacy of biventricular (BV) pacing in patients with standard indications for an ICD, symptomatic heart failure, a LVEF < or = 0.35, and a QRS > or = 120 ms. Patients underwent implantation of a BV pacing and sensing system with backup defibrillation capability, which includes a steroid-eluting coronary venous lead that is advanced into the coronary venous vasculature by over-the-wire techniques. LV pacing threshold, BV impedance, and BV R wave amplitude were measured in 58 consecutive patients. Using a percutaneous over-the-wire insertion technique, steroid-eluting coronary venous leads were associated with satisfactory mean LV pacing threshold, BV impedance, and BV R wave amplitude acutely up to 4 months after implantation. Pacing threshold stabilized 2 weeks after lead implantation and sensing threshold remained stable from the time of implant.

Cardiac Surgical Procedures↗
PubMed2000

Efficacy of biventricular sensing and treatment of ventricular arrhythmias.

While much is known concerning the hemodynamic effects of biventricular (BV) pacing, little has been reported concerning the efficacy of BV sensing and pacing in the detection and treatment of ventricular tachyarrhythmias. Two hundred nineteen heart failure (HF) patients with VT or VF and a QRS > or = 120 ms during sinus rhythm received an ICD capable of BV pacing and sensing. Detection times of induced VF and success rates for terminating induced VT were measured. The ICD system used a left ventricular epicardial lead implanted via thoracotomy (52 patients) or a specially designed percutaneous, over-the-wire lead inserted in the coronary venous system. VF detection times and VT termination rates by antitachycardia pacing (ATP) were compared with those measured in a population of recipients of ICD using a RV lead alone. Median induced VF detection times were comparable (2.0-s BV vs 1.8-s RV). Termination of induced VT on the first attempt was comparable with BV pacing (87.4%) versus RV pacing (89.6%). The time to detect induced VF was not different with ICDs using BV sensing versus conventional ICDs using RV sensing alone. Similarly, the rates of successful termination of induced VT by ATP with BV or RV pacing were comparable.

Cardiac Pacing, Artificial↗
PubMed1999

[Typical AV nodal reentry tachycardia in 4 anterograde AV nodal pathways. Successful high frequency ablation of slow AV nodal pathways].

CASE REPORT: A 26-year-old patient was referred to our department for electrophysiologic evaluation of recurrent paroxysmal tachycardias with narrow QRS-complexes (< 120 ms). Three jumps in the AV-nodal conduction curve were detected during programmed atrial extrastimulation in sinus rhythm and at a cycle length of 600 ms indicating of 4 antegrade conducting AV-nodal pathways. After intravenous application of orciprenaline an AV-nodal re-entrant-tachycardia (AVNRT) of the common type was induced with a cycle length of 290 ms. During tachycardia, antegrade conduction occurred via one of the slow conducting pathways, retrograde conduction via the fast pathway ("slow-fast"-AVNRT). Application of radiofrequency energy was able to ablate all slowly conducting AV-nodal pathways at one site in the infero-posterior region of Koch's triangle. During control stimulation with and without orciprenaline no AH-jump or inducible tachycardia was found. CONCLUSION: This case shows the rare finding of 4 antegrade AV-nodal pathways in a patient with the common type of AVNRT. Application of radiofrequency current was able to ablate all slow conducting AV-nodal pathways successfully.

Adult↗
PubMed1999

Single-chamber versus dual-chamber implantable cardioverter defibrillators: indications and clinical results.

The clinical benefit of standard (single-chamber) implantable cardioverter defibrillator (ICD) therapy in elderly patients or in subjects with moderate or severe heart failure who had ventricular tachyarrhythmias has been debated. We studied the follow-up of 450 patients who underwent standard ICD implantation at our institution in relation to the functional status of heart failure (New York Heart Association Class) or patient's age. During a mean follow-up of 24 +/- 28 months (range, < 1-114 months), 90 patients (23%) died: 9 patients (2%) from sudden arrhythmic death and 5 patients (1%) suddenly, but probably not from arrhythmic causes; 55 patients (14%) died from congestive heart failure and/or myocardial reinfarction and 21 patients (5%) from noncardiac causes. We could clearly demonstrate that ICD therapy was able to prevent sudden cardiac death, both in patients with severely depressed left ventricular function and in patients aged > or = 65 years. An important step forward in ICD technology was the introduction of dual-chamber pacing possibilities to improve left ventricular dysfunction and to allow a more individualized ICD therapy. At our institution, we have implanted a dual-chamber ICD in 15 patients. Preliminary results showed that heart failure improved in 5 patients (33%) and remained unchanged in 10 patients (67%, p = not significant). There were no patients who had a lesser degree of heart failure after implant. Based on our experience so far, in addition to the hemodynamic benefits of dual-chamber ICDs, dual-chamber sensing and wave-form storage capabilities are very helpful and promising diagnostic tools for the detection and handling of inappropriate ICD therapies.

Adult↗
PubMed1997

Age dependent efficacy of implantable cardioverter-defibrillator treatment: observations in 450 patients over an 11 year period.

OBJECTIVE: To determine whether implantable cardioverter-defibrillator (ICD) treatment is beneficial in elderly patients with life threatening ventricular tachyarrhythmias. DESIGN: Since January 1984, ICDs were implanted in 450 patients to evaluate surgical risk, complications and mean survival in relation to patient age; 81 patients (18%) were < or = 50 years at the time of ICD implant, 254 patients (56%) were between 51 and 64 years, and the remaining 115 (26%) were > or = 65 years. Epicardial lead systems were implanted in 209 patients (46%), while transvenous lead systems were implanted in 241 (54%). RESULTS: 13 patients (3%) died perioperatively, more often after epicardial (11 of 209 patients, 5%) than after transvenous ICD implantation (one of 241 patients, < 1%) (p < 0.05). During a mean (SD) follow up of 28 (24) months (range < 1 to 114 months), 90 patients (20%) died. Of these, nine (2%) died from sudden arrhythmic death; five (1%) died suddenly, probably as a result of non-arrhythmic causes; 55 (12%) died from other cardiac causes (congestive heart failure, myocardial infarction); and 21 (5%) died from non-cardiac causes. The three, five, and seven year survival for arrhythmic mortality was 95% in patients < or = 50 years compared with a three year survival of 93% and a five and seven year survival of 91% in patients of 51 to 64 years, and a three, five, and seven year survival of 99% in patients > or = 65 years. 362 patients (80%) received ICD discharges (21 (43) shocks per patient), with a similar incidence among all three patient groups (< or = 50 years, 80%; 51 to 64 years, 81%; > or = 65 years, 79%). The time interval between ICD implant and the first ICD treatment was shorter in patients > or = 65 years (8 (8) months) than in patients between 51 and 64 years (11 (14) months) or < or = 50 years (11 (11) months) (p < 0.05). Survival time following first appropriate shock was 30 (24) months in patients < or = 50 years, 30 (26) months in patients of 51 to 64 years, and 19 (20) months in patients > or = 65 years. CONCLUSIONS: Elderly patients benefit from ICD treatment, and survive for a considerable time after the first treatment. Therefore, elderly patients should be considered candidates for ICD implantation if life threatening ventricular tachy-arrhythmias are present.

Adolescent↗
PubMed1996

Stentless aortic valve replacement with the biocor prosthesis: indications and outcome.

BACKGROUND AND AIMS OF THE STUDY: Due to improved hemodynamic properties stentless bioprostheses represent a new therapeutic option in the surgical treatment of aortic valve disease. MATERIALS AND METHODS: Between February 1993 and June 1995 22 patients with a small aortic root regarded as suboptimal for a stented bioprosthesis (diameter < or = 23 mm, mean 21.6 +/- 1.9 mm) underwent aortic valve replacement with a Biocor stentless prosthesis. Mean age was 63.9 +/- 15.4 years (17-85 years). Valve size ranged from 21 to 27 mm (mean 25 mm) and exceeded the root diameter by 4 mm. As compared to a control group of patients with root enlargement (n = 10) total bypass time and cross-clamp time in the stentless group were significantly shorter (83.3 +/- 12.7 and 60.9 +/- 9.2 min versus 95.8 +/- 27.1 and 69.5 +/- 16.5 min, p = 0.054 and p < 0.05), respectively. RESULTS: Three patients died postoperatively unrelated to the choice of valve. There were no late deaths. No thromboembolic or bleeding events were observed. Follow up data are available over a period of 1-25 months (mean 12.5 months, median 16 months). Echocardiographic evaluation revealed no aortic regurgitation; mean valve gradients were 9.9 +/- 4.1 mmHg (peak 19.2 +/- 6.0 mmHg). For specific root diameters these gradients were compared to established data for Hancock bioprostheses demonstrating significant differences in transvalvular gradients between the two valve designs for given root diameters. Unloading the left ventricle resulted in regression of left ventricular hypertrophy (decrease in wall thickness from 13.6 +/- 1.7 mm to 11.2 +/- 2.0 mm). Exercise capacity improved from NYHA III-IV preoperative to I-II postoperative. CONCLUSIONS: In patients with a small aortic root stentless valves represent a new option. Compared to root enlargement with standard bioprosthesis myocardial ischemia is shorter and implantation of larger valve sizes results in superior hemodynamics.

Adolescent↗