Yasuo Ohkusu

Optimal Atrioventricular Delay Setting Determined by QT Sensor of Implanted DDDR Pacemaker

ISHIKAWA, T., et al.: Optimal Atrioventricular Delay Setting Determined by QT Sensor of Implanted DDDR Pacemaker. QT interval (QTI) may change when cardiac function is improved by optimizing the AV delay. QTI is used as the sensor for rate responsive pacemakers. Evoked (e)QTI is measured as the time duration from the ventricular pace‐pulse to the T sense point, which is the steepest point of the intracardiac T wave. The relationship between AV delay and eQTI and cardiac function was studied in 13 patients (74.2 ± 9.3 [SD] years old) with an implanted QT‐driven DDDR pacemaker. A special pacemaker software module was downloaded into the pacemaker memory for eQTI data logging. AV delay was set at 100, 120, 150, 180, 210, and 240 ms. Cardiac output (CO) was measured by continuous Doppler echocardiography. eQTI was 343.3 ± 22.4, 345.1 ± 22.5, and 343.4 ± 23.2 ms (P < 0.01, repeated ANOVA) and CO was 4.2 ± 0.8, 4.6 ± 0.8, and 4.2 ± 0.8 L/min (P < 0.0001, repeated ANOVA) when AV delay was set at the AV delay shortened by one step (AV[−]) and prolonged by one step (AV[+]) from the AV delay at which QT interval was maximum (AV[max]) in seven patients, in whom the peak AV delay at which the eQTI was maximal could be identified. eQTI decreased from 341.1 ± 20.9 to 339.4 ± 21.1 ms (P < 0.0001) and CO decreased from 4.4 ± 1.4 to 4.1 ± 1.3 L/min (P < 0.005) when AV delay was prolonged from AV(max) to AV(+) in all patients. eQTI decreased from 345.1 ± 22.5 to 343.3 ± 22.4 ms (P < 0.0005) and CO decreased from 4.6 ± 0.8 to 4.2 ± 0.8 L/min (P < 0.05) when AV delay was shortened from AV(max) to AV(−) in seven patients. Thus, CO was maximal when AV delay was set at the AV delay at which eQTI was maximal. In conclusion, the optimal AV delay can be predicted from the eQTI sensed by an implanted pacemaker, and automatic setting of the optimal AV delay can be achieved by the QT sensor of an implanted pacemaker.

Clinical usefulness of ECG-gated18F-FDG PET combined with99mTc-MIBI gated SPECT for evaluating myocardial viability and function

ObjectivesThis study sought to evaluate an imaging approach using gated99mTc-MIBI (MIBI) SPECT and gated18F-FDG (FDG) PET for assessment of myocardial viability and cardiac function.MethodsForty-eight patients (38 men, mean age 68.1 ± 9.6 years) underwent ECG-gated FDG PET and MIBI SPECT within a week. The baseline diagnoses were coronary artery disease (31), mitral regurgitation (1), paroxysmal arrhythmia (10), and dilated cardiomyopathy (6). The gated FDG PET data were analyzed using pFAST software, and the gated MIBI SPECT data were analyzed using QGS software. Fifteen patients were diagnosed with myocardial infarction, and follow-up study was performed to assess the functional outcome four months later. An improvement in LVEF of >5% was defined as significant. The LV myocardium was divided into 17 segments, and regional defect scores were visually assessed using a 4-point scale for each segment (0 = normal, 1 = mildly reduced, 2 = moderately reduced, 3 = absent). A segment with a greater defect score on MIBI SPECT than on FDG PET was defined as a mismatch. The patients were divided into two groups: those with at least two mismatched segments (MM-group), and those with none or one (M-group).ResultsLVEF, EDV and ESV measured by gated FDG PET were highly correlated with those obtained by gated MIBI SPECT (r = 0.848, 0.855 and 0.911, p < 0.0001, respectively). The mean values of LVEF did not differ significantly, but EDV and ESV obtained by gated FDG PET were significantly grater than those obtained by gated MIBI SPECT (p < 0.0001). In 15 patients diagnosed with myocardial infarction, a significant association (p < 0.05) was found between the relative uptake of FDG PET and MIBI SPECT and the functional outcome 4 months later. Global LV function improved in 6 of the 8 patients showing mismatch but in only 1 of the 7 patients with matched defects, resulting in a sensitivity of 86% and specificity of 75%. The overall accuracy to predict global functional outcome was high (80%).ConclusionThis imaging approach allows accurate evaluation of myocardial viability. Furthermore, the high correlations of gated FDG PET and gated MIBI SPECT measurements hold promise for the assessment of left ventricular function using gated FDG PET.

Effect of Biventricular Pacing on Myocardial Glucose Metabolism in Patients with Heart Failure Using Fluoro‐18‐Deoxyglucose Positron Emission Tomography

OHKUSU, Y., et al.: Effect of Biventricular Pacing on Myocardial Glucose Metabolism in Patients with Heart Failure Using Fluoro‐18‐Deoxyglucose Positron Emission Tomography. Biventricular pacing has recently been found beneficial in the treatment of congestive heart failure (CHF). Meanwhile, positron emission tomography (PET) has emerged as a new method to analyze glucose metabolism in the heart. Five patients (mean age 68.8 ± 8.1  years , 4 men) who received biventricular pacing therapy for 5.8 ± 6.6 weeks for CHF were studied. Myocardial glucose metabolism was evaluated by PET with fluoro‐18‐deoxyglucose (18F‐FDG), and percent uptake (%uptake) of 18F‐FDG was calculated during biventricular pacing and compared with that during 1 hour of conventional RV pacing. Biventricular pacing was associated with a significant decrease in NYHA functional Class from 3.67 ± 0.52 to 2.50 ± 0.55. After 18F‐FDG PET, three of five patients remained clinically stable, and two died during follow‐up. Mean 18F‐FDG %uptake during biventricular pacing was not different than during short‐term RV pacing ( 62.1 ± 18.4 vs. 63.6 ± 17.0% ). However, patients who remained clinically stable had a lower value of 18F‐FDG %uptake in the septal region than patients who died ( 46.9 ± 5.6 vs 80.3 ± 1.3%, P < 0.01 ). One patient whose cardiac function improved significantly also had a small septal region of decreased 18F‐FDG uptake during RV pacing. In conclusion, biventricular pacing therapy was effective in this small group of patients with severe, drug‐resistant CHF. An evaluation of the effects of biventricular pacing on glucose metabolism in the subacute phase may help identify patients with a favorable long‐term response to this therapy. (PACE 2003; 26[Pt. II]:144–147)

Assessment of regional wall motion by strain doppler during biventricular pacing in patients with conventional indications for a pacemaker

Biventricular pacing therapy is effective in patients with severe congestive heart failure. Strain Doppler imaging (SDI) is a new tool for measuring regional myocardial deformation. We evaluated regional wall motion by strain Doppler imaging in 13 patients who had conventional indications for a pacemaker (74 ± 6 years old) and in six with NYHA Class III or IV heart failure with a biventricular pacemaker (HF‐RV: during right ventricular pacing, HF‐BV: during biventricular pacing). The other seven patients had normal LV function (N‐RV). Wall motion was assessed by strain of the myocardium, and the interval between the Q wave of the surface ECG and the peak strain (QPSI) was measured in three septal and three lateral segments. Interventricular contraction delay was determined as the interval between the onset of the left and right ventricular outflow waves. Intraventricular contraction delay was determined as the time difference between minimum and maximum QPSI. Strain of HF‐RV was significantly greater than that of N‐RV (−9.6%± 2.5% vs −14.4%± 2.3%, P < 0.0001). Intraventricular contraction delay of HF‐RV was significantly greater than that of N‐RV (273 ± 12 vs 151 ± 69 ms, P = 0.0004). Strain of HF‐RV was not significantly greater than that of HF‐BV (−9.6%± 2.5% vs –10.6%± 2.9%). Interventricular contraction delay of HF‐RV was greater than that of HF‐BV (37.2 ± 44.7 vs 16.2 ± 47.4 ms, P < 0.0001). Intraventricular contraction delay of HF‐RV was significantly greater than that of HF‐BV (322 ± 101 vs 209 ± 88 ms, P = 0.0006). In conclusion, biventricular pacing improves both interventricular contraction delay and intraventricular contraction delay in patients with conventional indications for a pacemaker with severe congestive heart failure, and SDI is useful to predict the efficacy of biventricular pacing.

Anti-tachycardia therapy can improve altered cardiac adrenergic function in tachycardia-induced cardiomyopathy.

We investigated whether anti-tachycardia therapy might improve the altered cardiac adrenergic and systolic function in tachycardia-induced cardiomyopathy (TC) in contrast to dilated cardiomyopathy (DCM). The subjects were 23 patients with heart failure, consisting of 8 patients with TC (43.6±10.0 yrs) and 15 with DCM (45.3±8.2 yrs). TC was determined as impairment of left ventricular function secondary to chronic or very frequent arrhythmia during more than 10% of the day. All patients were receiving anti-tachycardia treatment. Cardiac123I-MIBG uptake was assessed as the heart/mediastinum activity ratio (H/M) before and after treatment. LVEF was also assessed. In the baseline study, H/M and LVEF showed no difference between TC and DCM (2.21 ±0.44 vs. 2.10±0.42, 35.3±13.1 vs. 36.0±10.9%, respectively). After treatment, the degree of change in H/M and LVEF differed significantly (0.41±0.34 vs. 0.08±0.20,20.5±14.4 vs. −2.1 ±9.6%, p<0.01). In TC, heart failure improved after a shorter duration of treatment (p<0.05). In conclusion, anti-tachycardia therapy can improve altered cardiac adrenergic function and systolic function in patients with TC over a shorter period than in those with DCM.