Biomedical subjects

Peter T Mortensen

Publications and source records attributed to Peter T Mortensen.

7 recordsLinked to original sources

PubMed2005

Monitoring of physical activity and heart rate variability in patients with chronic heart failure using cardiac resynchronization devices.

Cardiac resynchronization therapy (CRT) devices not only deliver effective treatment but may also serve as valuable diagnostic tools in heart failure management. In the present study, the minutes of daily physical activity and heart rate variability, measured by sensors incorporated into such a device, reflected the effects of CRT and were related to New York Heart Association functional class.

Aged↗

PubMed2005

Pacemaker implantation after congenital heart surgery: risk and prognosis in a population-based follow-up study.

OBJECTIVE: Although earlier a feared complication of congenital cardiac surgery, the incidence of heart-block and sinus node dysfunction has been lowered to 1-4% due to improved surgical techniques and better anatomical understanding of the cardiac conduction system. Development of feasible pacemaker technologies has further lowered mortality and morbidity. However, pacemaker implantation in paediatric patients is in itself associated with significant morbidity due to pacemaker system failure and replacement. The aim of the present study was to examine prognostic factors of mortality, failure of systems and timing of implantation after surgery in post-surgical pacemaker patients. METHODS: We carried out a historical prospective follow-up analysis of all patients (age less than 18 years) who underwent pacemaker implantation due to post-surgical heart-block or sinus node dysfunction in the period 1981-2002 at our institution. Data was extracted from the Danish Pacemaker Register and hospital records. Kaplan-Meier survival time estimates and Cox proportional hazards analysis (Relative Risk, RR) were used to identify prognostic factors. RESULTS: High RACHS score (RR, 16.57), low age at implantation (RR, 0.22), low age at operation (RR, 0.06) and epicardial lead (RR, 0.18) were significant predictors for early mortality. Similarly, high RACHS score (RR, 4.84), low age at implantation (RR, 0.32), low age operation (RR, 0.38) and epicardial lead (RR, 0.40) were significant predictors failure of 1st pacemaker system. CONCLUSIONS: We identified a number of prognostic factors of patient mortality and failure of systems. One factor, high RACHS score, was previously shown to predict mortality and length of ICU stay in paediatric cardiac surgery; however, this study is the first to show a correlation between RACHS score and mortality as well as failure of pacemaker systems. This may have future implications for preoperative risk stratification of patients and counselling of parents to patients with congenital heart disease.

Adolescent↗

PubMed2005

Ablation of atrial tachycardia after surgery for congenital and acquired heart disease using an electroanatomic mapping system: Which circuits to expect in which substrate?

OBJECTIVES: The purpose of this study was to compare atrial tachycardia circuits after a range of cardiac operations. BACKGROUND: Knowledge of circuits occurring in a given postsurgical substrate should help to ablate these challenging tachycardias and develop potential preventive strategies. METHODS: We analyzed tachycardia circuits in 83 consecutive patients (60 males; median age 47 years, range 9-73) after atrial incisions undergoing ablation of atrial tachycardias. A combined strategy of electroanatomic (CARTO) and entrainment mapping was used. Fifty-two patients (63%) underwent operation for congenital and 31 (37%) for acquired heart disease. Patients were divided into subgroups based on the intervention performed in the atria: right lateral atriotomy (39 patients), left atrial (11) and superior transseptal (10) approach to the mitral valve, biatrial heart transplantation (8), Mustard (8) and Fontan (4) procedure, and other interventions (3). RESULTS: Most of the 119 tachycardias mapped were isthmus-dependent atrial flutter (66) and incisional tachycardia (30). Isthmus-dependent atrial flutter was the most frequent arrhythmia in all subgroups except for Fontan patients, in whom incisional tachycardia was most frequent. The distribution of tachycardia circuits did not differ significantly among groups. CONCLUSIONS: The observed circuits did not differ among the postsurgical substrates. Isthmus-dependent atrial flutter should be the first circuit considered in patients after atrial incisions.

Atrial Flutter↗

PubMed2004

Sequential biventricular pacing: evaluation of safety and efficacy.

The study evaluated the clinical safety, performance, and efficacy of sequential biventricular pacing in the InSync III (Model 8042) biventricular stimulator in a multicenter, prospective 3-month study and assessed the proper functioning of features aiming at improving biventricular AV therapy delivery. The system was successfully implanted in 189 (95.9%) of 198 patients with symptomatic systolic heart failure and a prolonged QRS complex duration. Patients significantly improved their 6-minute hall walk distance (baseline 339 +/- 92 vs 3-month 422 +/- 127 meter, P < 0.001) and NYHA class (baseline 3.1 +/- 0.5 vs 3-month 1.9 +/- 0.7, P < 0.001). Echocardiographic optimization of sequential biventricular pacing showed an improvement in stroke volume compared to simultaneous stimulation (sequential 68 +/- 24 mL vs simultaneous 56 +/- 23 mL, P < 0.001) at baseline and at 3 months. In 88% (30/34) of the patients these improvements were seen within a small range of V-V delays of +/-20 ms and in 94% (32/34) within V-V delays of +/-40 ms. In contrast, programming beyond this range reduced stroke volume below that during simultaneous biventricular pacing. The device functioned as expected. LV lead dislodgement was observed in 12 patients and phrenic nerve stimulation required lead repositioning in 2 patients. Eight patients died during the study. Patient survival at 3 and 6 months was 97 +/- 2% and 94 +/- 2%, respectively. Cause of death was cardiac (n = 7), heart failure related (n = 3), arrhythmia related (n = 2), and unknown (n = 2). In conclusion, this sequential biventricular pacemaker was safe and efficacious.

Aged↗

PubMed2003

A randomized comparison of atrial and dual-chamber pacing in 177 consecutive patients with sick sinus syndrome: echocardiographic and clinical outcome.

OBJECTIVES: A randomized trial was done to compare single-chamber atrial (AAI) and dual-chamber (DDD) pacing in patients with sick sinus syndrome (SSS). Primary end points were changes in left atrial (LA) size and left ventricular (LV) size and function as measured by M-mode echocardiography. BACKGROUND: In patients with SSS and normal atrioventricular conduction, it is still not clear whether the optimal pacing mode is AAI or DDD pacing. METHODS: A total of 177 consecutive patients (mean age 74 +/- 9 years, 73 men) were randomized to treatment with one of three rate-adaptive (R) pacemakers: AAIR (n = 54), DDDR with a short atrioventricular delay (n = 60) (DDDR-s), or DDDR with a fixed long atrioventricular delay (n = 63) (DDDR-l). Before pacemaker implantation and at each follow-up, M-mode echocardiography was done to measure LA and LV diameters. Left ventricular fractional shortening (LVFS) was calculated. Analysis was on an intention-to-treat basis. RESULTS: Mean follow-up was 2.9 +/- 1.1 years. In the AAIR group, no significant changes were observed in LA or LV diameters or LVFS from baseline to last follow-up. In both DDDR groups, LA diameter increased significantly (p < 0.05), and in the DDDR-s group, LVFS decreased significantly (p < 0.01). Atrial fibrillation was significantly less common in the AAIR group, 7.4% versus 23.3% in the DDDR-s group versus 17.5% in the DDDR-l group (p = 0.03, log-rank test). Mortality, thromboembolism, and congestive heart failure did not differ between groups. CONCLUSIONS: During a mean follow-up of 2.9 +/- 1.1 years, DDDR pacing causes increased LA diameter, and DDDR pacing with a short atrioventricular delay also causes decreased LVFS. No changes occur in LA or LV diameters or LVFS during AAIR pacing. Atrial fibrillation is significantly less common during AAIR pacing.

Aged↗

PubMed2002

Sequential versus simultaneous biventricular resynchronization for severe heart failure: evaluation by tissue Doppler imaging.

BACKGROUND: Cardiac resynchronization therapy (CRT) by means of simultaneous biventricular pacing improves left ventricular systolic performance and synchrony in patients with heart failure and bundle-branch block. We used tissue tracking and 3D echocardiography to evaluate the impact of sequential CRT with individualized interventricular delay programming. METHODS AND RESULTS: Twenty consecutive patients with severe heart failure and left bundle-branch block were included. Tissue tracking and 3D echocardiography were carried out before and on the day after pacemaker implantation. Eleven different interventricular delays were examined in each patient. Patients were reexamined after 3 months. Simultaneous CRT immediately reduced the extent of myocardium displaying delayed longitudinal contraction (DLC) from 48.6+/-16% to 23.2+/-13% (P<0.01) and increased left ventricular ejection fraction percentage (LVEF%) from 22.4+/-6% to 29.7+/-5% (P<0.01). However, optimum sequential CRT caused a further reduction in the extent of DLC from 23.2+/-13% to 11.1+/-7.2% (P<0.01), with a simultaneous increase in LVEF% (from 29.7+/-5% to 33.9+/-6%, P<0.01). Three months of optimum sequential CRT further improved LVEF% (from 33.6+/-6% to 38.6+/-7.2%, P<0.01). Tissue tracking detected the segments with DLC, and their location determined optimum interventricular delay programming. Compared with simultaneous CRT, sequential CRT increased diastolic filling time by 7+/-2.5%. CONCLUSIONS: Compared with simultaneous CRT, sequential CRT significantly improves left ventricular systolic and diastolic performance. Tissue tracking can be used to select optimum interventricular delay during CRT.

Aged↗

PubMed2002

Tissue Doppler imaging predicts improved systolic performance and reversed left ventricular remodeling during long-term cardiac resynchronization therapy.

OBJECTIVES: We sought to evaluate the long-term impact of cardiac resynchronization therapy (CRT) on left ventricular (LV) performance and remodeling using three-dimensional echocardiography and tissue Doppler imaging (TDI). BACKGROUND: Three-dimensional echocardiography and TDI allow rapid and accurate evaluation of LV volumes and performance. METHODS: Twenty-five consecutive patients with severe heart failure and bundle branch block who underwent biventricular pacemaker implantation were included. Before and after implantation of the pacemaker, three-dimensional echocardiography and TDI were performed. These examinations were repeated at outpatient visits every six months. RESULTS: Five patients (20%) died during one-year follow-up. In the remaining 20 patients, significant reductions in LV end-diastolic volume and LV end-systolic volume of 9.6 +/- 14% and 16.5 +/- 15%, respectively (p < 0.01), could be demonstrated during long-term follow-up. Accordingly, LV ejection fraction increased by 21.7 +/- 18% (p < 0.01). According to a newly developed TDI technique-tissue tracking-all regional myocardial segments improved their longitudinal systolic shortening (p < 0.01). The extent of the LV base displaying delayed longitudinal contraction, as detected by TDI before pacemaker implantation, predicted long-term efficacy of CRT. The QRS duration failed to predict resynchronization efficacy. CONCLUSIONS: Cardiac resynchronization significantly improved LV function and reversed LV remodeling during long-term follow-up. Patients likely to benefit from CRT can be identified by TDI before implantation of a biventricular pacemaker.

Bundle-Branch Block↗