Long-term follow-up of atrioventricular delay optimization in patients with biventricular pacing.

BACKGROUND: Atrioventricular (AV) delay optimization may be important in patients with biventricular pacing and the optimal AV delay can be predicted using Doppler echocardiography and the formula: optimal AV delay = AV delay-the interval between the end of A wave and complete closure of the mitral valve when the AV delay is set at slightly prolonged AV delay. METHODS AND RESULTS: In the present study the efficacy of this method was evaluated in 5 patients (67.4+/-8.0 (SD) years old) with biventricular pacing. Cardiac output (CO) and diastolic filling time were measured by Doppler echocardiography. When the AV delay was set at the predicted optimal AV delay -25 ms, the predicted optimal AV delay (133+/-66 ms) and predicted optimal AV delay + 25 ms, the respective CO were 4.5+/-0.9, 5.3+/-1.0, 4.8+/-1.0 L/min (p<0.05, ANOVA) and the diastolic filling times were 364 +/-100, 373+/-105, 335+/-84 ms (p<0.05, ANOVA). Congestive heart failure improved from New York Heart Association class 3.6+/-0.5 to 1.4+/-0.5 (p<0.001). CONCLUSIONS: AV delay optimization is important in patients with biventricular pacing and can be easily achieved by the new method.

Clinical usefulness of ECG-gated 18F-FDG PET combined with 99mTC-MIBI gated SPECT for evaluating myocardial viability and function.

OBJECTIVES: This study sought to evaluate an imaging approach using gated 99mTc-MIBI (MIBI) SPECT and gated 18F-FDG (FDG) PET for assessment of myocardial viability and cardiac function. METHODS: Forty-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). RESULTS: LVEF, 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%). CONCLUSION: This 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.

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.

Prevalence of right bundle-branch block and right precordial ST-segment elevation (Brugada-type electrocardiogram) in Japanese children.

BACKGROUND: The prevalence of Brugada-type electrocardiogram (ECG) in schoolchildren remains unclear. This study aimed to further investigate this condition. METHODS AND RESULTS: We studied the prevalence of Brugada-type ECG in 20,387 children (10,434 males and 9,953 females, 9.7 +/- 3.2 [SD] years old) during a school health examination in Kanagawa Prefecture, Japan, in 2002. We considered right bundle-branch block and ST-segment elevation of the J point of > or =0.1 mV in leads V1 through V3 as Brugada-like ECG, and an ECG was considered to be Brugada-type when the 12-lead ECG fully meet the criteria for the Brugada syndrome as recently published in a consensus report. Only 2 children (0.0098%, 95% confidence interval (CI): 0 to 0.023%) completely conformed to the criteria for Brugada-type ECG. Brugada-like ECG was found in 11 (10 male) of 20,387 children (0.054%, 95% CI: 0.022 to 0.086%). The prevalence in males was significantly higher than that in females, even in children (0.096% vs 0.010%, p=0.012). Stratified according to age, there was tendency for the prevalence of Brugada-like ECG to increase up to puberty (first graders, 0.01%; fourth graders, 0.05%; seventh graders, 0.08%; tenth graders, 0.23%; p=0.068). CONCLUSION: The prevalence of Brugada-type ECG in Japanese children was much lower than that reported in the adult population.

Double-counting of intracardiac electrogram during biatrial pacing.

BACKGROUND: Biatrial pacing has a significant problem with memory function that misinterprets normal sinus rhythm as atrial tachyarrhythmias and in addition estimation of the atrial pacing thresholds (biatrial and uniatrial pacing thresholds) is sometimes difficult because of small P waves. METHODS AND RESULTS: The intracardiac electrograms recorded by a pacemaker in 10 patients (age, 66.7+/-10.7 (SD) years) with implanted biatrial pacemakers were analyzed. Atrial sensing within the atrial refractory period after atrial pacing was counted in 6 of the 10 patients (timing of the double counting was 143+/-64 ms) when pacing failed in the left or right atrium. Atrial sensing within the atrial refractory period after atrial pacing disappeared when biatrial pacing was successfully performed. Atrial double-counts depend on interatrial conduction delay. The memory function of implanted pacemaker devices misinterpreted normal sinus rhythm as atrial tachyarrhythmias because of atrial double-counts. On the other hand, the biatrial pacing threshold was easily recognized using this phenomenon. CONCLUSIONS: The memory function of pacemaker devices is unreliable because of atrial double-counting during sinus rhythm in patients with biatrial pacing. However, the biatrial pacing threshold is easily checked using this phenomenon.

[Brugada syndrome associated with ventricular fibrillation induced by administration of pilsicainide: a case report].

A 56-year-old man with Brugada syndrome presented with ventricular fibrillation induced by administration of pilsicainide. He had syncope at age 46 years, and his uncle suddenly died of unknown cause. He had taken pilsicainide (150 mg/day) for paroxysmal atrial fibrillation, and suffered from syncope due to ventricular fibrillation. Coved type ST elevation was observed in the V1 lead, and saddle back type ST elevation was observed in the V2 lead. The ST elevation gradually recovered after stopping pilsicainide therapy. No structural heart disease was found. After intravenous injection of pilsicainide, the ST segment elevated in the V1 and V2 leads. Ventricular fibrillation was induced by triple extrastimulation at the right ventricular apex. The diagnosis was Brugada syndrome, and a cardioverter-defibrillator was implanted. Brugada syndrome should be considered before administering pilsicainide.

[Factors for successful conversion of atrial fibrillation using intravenous injection of pilsicainide hydrochloride].

OBJECTIVES: The factors affecting successful conversion of atrial fibrillation using intravenous injection of pilsicainide hydrochloride are unclear. The efficacy of intravenous injection of pilsicainide hydrochloride and the factors affecting successful conversion of symptomatic atrial fibrillation were investigated. METHODS: Twenty-six patients[21 men, 5 women, 64 +/- 12 years (mean +/- SD)] with electrocardiographically confirmed, symptomatic atrial fibrillation were treated with intravenous injection 1.0 mg/kg of pilsicainide hydrochloride between October 31, 2000 and February 17, 2003. Successful conversion was defined as termination of atrial fibrillation within 30 min of intravenous injection. Before the injection of pilsicainide hydrochloride, blood pressure, conventional electrocardiography, chest radiography, echocardiography and blood examinations were performed. During and after injection of pilsicainide hydrochloride, blood pressure and conventional electrocardiography were monitored. After injection of pilsicainide hydrochloride, blood examinations were performed. RESULTS: Pharmacological conversion to sinus rhythm was achieved in 7 of 26 patients(27%). The successful conversion group and unsuccessful conversion group showed significant differences in duration of atrial fibrillation(61 +/- 122 vs 12,257 +/- 25,959 hr, p < 0.01), heart rates before injection of pilsicainide (110 +/- 26 vs 87 +/- 26 beats/min, p < 0.05), cardiothoracic ratio(47.8 +/- 2.6% vs 53.5 +/- 5.1%, p < 0.01) and left atrial dimension(38 +/- 7 vs 45 +/- 6 mm, p < 0.05). CONCLUSIONS: Pilsicainide hydrochloride is effective in patients with atrial fibrillation of short duration with small left atrium and rapid ventricular response.

Changes in evoked QT intervals according to variations in atrioventricular delay and cardiac function in patients with implanted QT-driven DDDR pacemakers.

In patients with implanted DDD pacemaker, cardiac output is maximal when atrioventricular (AV) delay is set to give the maximum QT interval (QTI). QTI is used as a sensor of a rate-responsive pacemaker and the evoked QTI (eQTI) is measured as the time duration from the ventricular pace-pulse and the T sense point, which is the steepest point of the intracardiac T wave. The relationship between the changes in eQTI according to AV delay variations and cardiac function was studied in 13 patients (74.2+/-9.3 [SD] years old) with an implanted QT-driven DDDR-pacemaker. A special software module was downloaded into the pacemaker memory and a personal computer equipped with the special software was connected to the programmer for eQTI date-logging. AV delay was set at 100, 120, 150, 180 and 210 ms. Delta eQTI was defined as maximal eQTI - minimal eQTI. The ejection fraction (EF) was measured by echocardiography. When the AV delay was prolonged, eQTI gradually increased and reached a peak, and then decreased. Delta eQTI in patients with reduced cardiac function (EF <40%) was significantly greater than that in normal cardiac function (EF >55%, 7.6+/-4.9 vs 2.7+/-9.8 ms, p<0.05). There was significant negative correlation between EF and delta eQTI (r=-0.63, p<0.05). The peak of changes in eQTI according to AV delay variations was steeper in patients with reduced cardiac function than in those with normal cardiac function. In conclusion, changes in eQTI according to AV delay variation are greater in patients with reduced cardiac function than in those with normal cardiac function, and the AV delay that gives the maximal eQTI can be easily determined in patients with reduced cardiac function.

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.

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.

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. Cardiac 123I-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.