Assessing Acute Ventricular Volume Changes by Intracardiac Impedance in a Chronic Heart Failure Animal Model

Background: Implantable device diagnostics may play an essential role in simplifying the care of heart failure patients by providing fundamental insights into their complex clinical patterns. Early recognition of heart failure progression by a continuous hemodynamic monitoring would allow for timely therapeutic interventions to prevent decompensation and hospitalization. In this study, the feasibility of assessing ventricular volume changes by implant-based measurements of intracardiac impedance was tested in a heart failure animal model.
Methods: Heart failure was induced in five minipigs by high-rate pacing over 3 weeks. During a final open-chest examination a graded dobutamine stress test was performed. Stroke volume (SV) was measured by an ultrasonic flow probe at the ascending aorta. End diastolic pressure (EDP) and maximum pressure slope (dP/dt_max) were calculated from a left ventricular microtip catheter signal. Impedance was measured by an implanted pacemaker between biventricular leads. Stroke impedance (SZ) was calculated as the difference between end-systolic and end-diastolic impedance (EDZ).
Results: Administration of dobutamine led to an increase in SV (55 ± 16%), dP/dt_max (107 ± 89%), and SZ (56 ± 30%). EDP changed by 37 ± 21% whereas EDZ changed by 7.4 ± 4%. Significant correlations were found between SZ and SV (r = 0.88), and between EDZ and EDP (r =−0.82).
Conclusion: The strong correlation with SV allows the application of intracardiac impedance measurements for an implant-based continuous monitoring of cardiac function. Impedance may also be used for hemodynamic optimization of cardiac resynchronization therapy.     

Predictors of Atrial Tachyarrhythmias in Subjects with Type 1 ECG Pattern of Brugada Syndrome

Background: Previous studies have demonstrated a high incidence of atrial tachyarrhythmias (ATs) in patients with Brugada syndrome (BS). The present study aimed to investigate whether various 12-lead electrocardiogram (ECG) and electrophysiological parameters may help to differentiate subjects with a high probability to develop ATs.
Methods and Results: The clinical records of 38 individuals (31 males, age 44.4 ± 13.9) with spontaneous (n = 15) or ajmaline-induced (n = 23) type 1 ECG pattern of BS were analyzed. During a mean follow-up period of 4.6 ± 2.2 years, nine subjects suffered ATs (24%). Six subjects displayed paroxysmal atrial fibrillation and three typical atrial flutter. Among the studied 12-lead ECG parameters, subjects with ATs exhibited increased values of P-wave duration in lead II, P-wave dispersion, PR interval in leads II, QRS duration in leads II and V₂, Tpeak-end interval in lead II, and Tpeak-end dispersion of the 12 leads in relation to those without ATs (P < 0.05). Among the assessed electrophysiological parameters, atrial-His (AH) and His-ventricular (HV) intervals were significantly prolonged in subjects with ATs (P < 0.05). Multiple Cox proportional hazards analysis revealed that P-wave duration in lead II, P-wave dispersion, Tpeak-end in lead II, Tpeak-end dispersion of the 12 leads, as well as AH and HV intervals are independent predictors of ATs in subjects with BS (P < 0.05). Cut-off point analysis showed that an HV interval ≥ 56 ms displayed the highest predictive ability (P < 0.01).
Conclusion: Our findings demonstrate that simple 12-lead ECG and electrophysiological parameters may easily be applied to identify high-risk subjects with BS ECG phenotype to develop ATs .     

Role of Left Ventricular Scar and Purkinje‐Like Potentials During Mapping and Ablation of Ventricular Fibrillation in Dilated Cardiomyopathy

Background: Purkinje‐like potentials (PLPs) have been described as important contributors to initiation of ventricular fibrillation (VF) in patients with normal hearts, ischemic cardiomyopathy, and early after‐myocardial infarction. Methods: Of the 11 consecutive patients with VF storm, nonischemic cardiomyopathy (68 ± 22 years, left ventricular ejection fraction 28 ± 8%) who were given antiarrhythmic drugs and/or heart failure management, five had recurrent VF and underwent electrophysiology study (EPS) and catheter ablation. Results: At EPS, frequent monomorphic premature ventricular contractions (PVC) and/or ventricular tachycardia did not occur. With isoproterenol, VF was induced in three patients, and sustained monomorphic PVCs were induced in one patient. Three‐dimensional electroanatomical mapping using CARTO (Biosense‐Webster Inc., Diamond Bar, CA) revealed posterior wall scar in four of the five patients. PLP in sinus rhythm were recorded around the scar border in these four patients, and radiofrequency ablation targeting PLP was successfully performed at these sites. The patient without PLP did not undergo ablation. During follow‐up (12 ± 5 months), only the patient without PLP had four VF recurrences requiring implantable cardioverter‐defibrillator (ICD) shocks. Conclusion: In patients with VF and dilated cardiomyopathy, left ventricular posterior wall scar in the vicinity of the mitral annulus seems to be a common finding. Targeting PLP along the scar border zone for ablation seems to efficiently prevent VF recurrence in these patients.     

Primary Prevention of Atrial Fibrillation: Does the Atrial Lead Position Influence the Incidence of Atrial Arrhythmias in Patients with Sinus Node Dysfunction? Results from the PASTA Trial

Introduction: PASTA (pacing of the atria in sinus node disease) is a prospective and randomized trial, assessing the effect of different atrial lead positions on the atrial fibrillation (AF) incidence in patients with sinus node disease (SND). Method: The atrial lead position is randomized to: (a) free right atrial wall, (b) right atrial appendage (RAA), (c) coronary sinus ostium (CS‐Os), or (d) dual site right atrial pacing (CS‐Os + RAA). The pacemakers (Vitatron Selection 9000 or Prevent AF, Vitatron B.V., Arnhem, The Netherlands) are programmed in DDDR 70 mode and the total follow‐up duration is 24 months. To describe the atrial rhythm state, pacemaker‐derived data (arrhythmia counter) were assessed for AF episodes. AF was considered as evident, if the AF burden (time in AF related to follow‐up interval) was >1% (i.e., 15 min/d). Follow‐up data after 24 months were evaluated. Results: The analysis evaluates 142 patients (77 male, 74.5 ± 7.8 years). There was no statistical significant difference with respect to the occurrence of AF between the four groups after 24 months (A: 36%; B: 38%, C: 32%, D: 48%). The percentage of atrial/ventricular pacing was in A: 78/76%, in B: 84/81%, in C: 70/65%, and in D: 79/69%. These differences were not significant. Conclusion: The evaluation of the AF burden >1% and the total AF burden after 24 months did not show differences in the incidence of AF in patients with dual chamber pacemaker therapy for SND. We were not able to demonstrate a significant influence of right atrial lead position on the incidence of AF recurrence.     

ICAM-1基因Gly214Arg多态性与缺血性脑卒中的关系

目的　探讨中国人缺血性脑卒中与细胞间粘附分子 1(IntercellularAdhesionMolecule 1,ICAM 1)基因Gly 2 14Arg多态性之间的关系。方法　利用PCR技术和分子杂交技术对北京地区 2 94例缺血性脑卒中患者进行ICAM 1基因Gly2 14Arg多态性的检测和分析 ,并与 2 79例北京地区的非卒中对照进行比较。 结果　缺血性脑卒中患者ICAM 1基因Gly2 14Arg多态性的基因型频率和等位基因频率与对照组相比无明显差异。结论　ICAM 1基因Gly 2 14Arg多态性可能不是中国人群缺血性脑卒中发病的遗传学危险因素。     

Need for Fast Pathway Ablation in Typical Irregular AV Nodal Reentrant Tachycardia in a Patient with Multiple AV Nodal Pathways

A case of a 60-year-old male with irregular AV nodal reentrant tachycardia of the common type is reported. Electrophysiological study revealed multiple antegrade slowly conducting AV nodal pathways and one exclusively retrogradely conducting fast AV nodal pathway. Despite the recommendation for slow pathway ablation as the treatment of choice in patients with AVNRT, first pathway ablation was successfully performed in this case due to the risk of total A V block of ablating the slow pathways. The present report shows that there is the rare patient in whom fast pathway ablation is required for curative treatment of AV nodal reentrant tachycardia.     

Asymptomatic Pulmonary Embolism Following Pacemaker Implantation

The aim of this prospective study was to investigate the incidence of pulmonary embolism after pacemaker implantation, and to assess the benefits, if any, of postoperative prophylactic heparin therapy. Twenty of 40 patients were given low-dose heparin therapy; the remaining 20 patients were the control group and were not treated. Assignment to one of these groups was made alternately, in chronological order according to the time of implantation. Only tined leads with silicone insulation were used. All patients were mobilized on their first postoperative day. Pulmonary scintigraphy was performed before implantation, two weeks after implantation and again 12 months later. A pulmonary embolism was defined as evidence of new perfusion defects after implantation. There were no such defects in the group treated with heparin; the control group (20 patients) had three cases of perfusion defects within a 14-day postoperative period. Twelve months later, no further perfusion defects were observed in any patient. Thus, our study revealed a 15% incidence of asymptomatic pulmonary embolism following pacemaker implantation in patients not given prophylactic heparin therapy.