RIGHT VENTRICLE LEAD IMPEDANCE IN PATIENTS WITH IMPLANTED DEFIBRILLATING DEVICES CORRELATES WITH THEIR CLINICAL CONDITION
The electrical impedance is the opposition to the current flow and it measures the total resistance to such flow. The lead impedance for implanted devices is a function of various properties of the electrode and the myocardium. This study aimed at the evaluation of the relation between the right ventricle (RV) lead impedance and parameters quantifying clinical condition in patients with implanted defibrillating devices.
The study was performed in a group of 400 consecutive patients (63.0+/-10 years; 77 women) with an already implanted cardioverter-defibrillator or a cardiac resynchronization therapy device with defibrillating mode. The RV lead impedance was measured by a telemetry during a routine and elective device check-up. All patients underwent a routine cardiac examination including echocardiography, the 6-minute walking test (6MWT), and the plasma N-terminal-pro-Brain natriurectic peptide (NT-pro-BNP) level measurement in venous blood samples. For statistical purposes the NT-pro-BNP level was normalized with natural logarithm. Patients were divided into tertiles (T1, T2 or T3) of the RV lead impedance, and analysis of variance with the Bonferroni post-tests were applied for statistical analysis.
The results of clinical evaluation are shown in Table 51.1. Patients from the highest RV lead impedance tertile had a significantly lower level of NTpro-BNP, smaller areas of right atrium, right ventricle and left atrium than patients from T1 and T2. Additionally, T3 patients had a significantly longer total distance of the 6MWT and larger left ventricular ejection fraction than patients from T1 of RV lead impedance.
Conclusions: The electrical impedance of the right ventricular lead in patients with implanted defibrillating device is significantly associated with the cardiac clinical status. Patients with the highest values of RV lead impedance present with a much better cardiac condition, i.e. have significantly smaller sizes of right heart chambers, longer distance of the 6MWT, higher values of left ventricular ejection fraction and less elevated NT-pro-BNP plasma concentration. Further studies are required to answer the question whether the measurements of the RV lead impedance might be applied for a prospective evaluation of the clinical condition and monitoring of patients with implanted defibrillating devices.