Hidekazu Hirao

Frequency-dependent electrophysiologic properties of ventricular repolarization in patients with congenital long QT syndrome

OBJECTIVES This study was performed to evaluate the frequency dependency of ventricular repolarization and the effect of epinephrine in patients with congenital long QT syndrome (LQTS). BACKGROUND The efficacy of pacemakers in addition to antiadrenergic therapy in the treatment of congenital LQTS has been reported. METHODS Monophasic action potentials were recorded from right and left ventricular endocardium during atrial pacing at heart rates from 70 to 140 beats/min at baseline and from 100 to 140 beats/min during epinephrine infusion (0.1 microgram/kg body weight per min) in 11 patients with congenital LQTS and 10 control patients. The response of monophasic action potential duration at 90% repolarization (MAPD90) and the dispersion of MAPD90 were examined. RESULTS At baseline, both the MAPD90 and the dispersion of MAPD90 were significantly (p < 0.001) longer in the congenital LQTS group than the control group. The differences in these variables between the two groups significantly decreased (MAPD90: from 105 to 31 ms; dispersion of MAPD90: from 55 to 13 ms, p < 0.001) at heart rate was increased. Epinephrine prolonged the MAPD90 and increased the dispersion of MAPD90 significantly (p < 0.001) at all paced heart rates in the congenital LQTS group without frequency dependency but did not change in the control group. Thus, epinephrine increased the differences in these variables between the two groups. CONCLUSIONS The repolarization abnormalities in congenital LQTS were attenuated by increasing the heart rate, which supported the efficacy of pacemaker therapy. However, during sympathetic stimulation, the effects of increased heart rate on these repolarization abnormalities were limited.

Calorie restriction reduced blood pressure in obesity hypertensives by improvement of autonomic nerve activity and insulin sensitivity.

Summary: Association between obesity and hypertension has been well recognized. A reduction in the body weight of overweight hypertensive patients is a recommended lifestyle modification. The purpose of our study is to examine the relationship of insulin sensitivity and autonomic nervous activity with reduction of blood pressure by the calorie restriction. We evaluated the heart rate variability, nocturnal change of blood pressure and insulin resistance before and after a short‐term low‐calorie diet in 12 overweight essential hypertensives. After a week of standard diet (2000 kcal), 2 weeks of low‐calorie diet (800 kcal) with normal sodium content induced a significant reduction in body mass index, triglyceride, fasting immunoreactive protein, homeostasis model assessment as an index of insulin resistance, and urinary excretion of sodium and potassium. Systolic blood pressure was significantly reduced both in daytime and night‐time after the low‐calorie diet (daytime, 134.5 ± 6.0 to 122.0 ± 4.1 mmHg; night‐time, 126.8 ± 5.2 to 113.4 ± 7.2 mmHg). In daytime, diastolic blood pressure was also reduced (90.3 ± 2.1 to 88.1 ± 4.8 mmHg). Although heart rate was not significantly reduced, a rise of high frequency in night‐time (346 ± 82 to 572 ± 108 ms2) and a fall of low frequency/high frequency in daytime (3.5 ± 0.4 to 2.6 ± 0.1) was significant after a low‐calorie diet. In conclusion, weight loss by low‐calorie diet with a constant intake of sodium, reduced blood pressure in obese hypertensives by improvement of vagal nervous activity and insulin resistance.

Relation between QT dispersion and adenosine triphosphate stress thallium-201 single-photon emission computed tomographic imaging for detecting myocardial ischemia and scar

It is not known if QT dispersion is useful for detecting coronary artery disease. We investigated whether QT dispersion at baseline and during adenosine triphosphate (ATP) infusion correlate with the imaging patterns obtained from ATP stress thallium-201 single-photon emission computed tomography (ATP-SPECT). QT dispersion was determined in 169 patients who underwent ATP-SPECT from 12-lead electrocardiograms obtained at baseline and 3 minutes after the beginning of ATP infusion. Based on the results of ATP-SPECT, patients were divided into 4 groups: normal (n = 55), ischemia (n = 38), ischemia and scar (n = 42), and scar (n = 34). Baseline QT dispersions (mean +/- SD) in the normal, ischemia, ischemia and scar, and scar groups were 48 +/- 15, 50 +/- 17, 69 +/- 25, and 70 +/- 24 ms, respectively. Baseline QT dispersion was significantly greater in the groups with myocardial scar. QT dispersions during ATP infusion were 43 +/- 16, 63 +/- 20, 76 +/- 20, and 62 +/- 25 ms in the normal, ischemia, ischemia and scar, and scar groups, respectively. QT dispersion increased with ATP infusion in patients with myocardial ischemia. QT dispersion at baseline and during ATP infusion correlated with the ATP-SPECT imaging pattern. These findings suggest that baseline QT dispersion and ATP-induced changes in QT dispersion may help detect the presence of myocardial ischemia and scar.

Exogenous adenosine triphosphate disodium administration during primary percutaneous coronary intervention reduces no-reflow and preserves left ventricular function in patients with acute anterior myocardial infarction: A study using myocardial contrast echocardiography

BACKGROUND It is unknown whether adenosine triphosphate disodium (ATP) administration during primary percutaneous coronary intervention (PCI) is useful in anterior acute myocardial infarction (AMI). METHODS The study was a prospective, non-randomized, open-label trial. Primary PCI was successfully performed in 204 consecutive patients with first anterior AMI. ATP at a mean dose of 117 microg/kg/min for 45 min on an average was infused intravenously during PCI in 100 patients (Group 1). In the other 104 patients, normal saline was administered (Group 2). ST-segment resolution (STR) was estimated 90 min after recanalization. The no-reflow ratio was measured 2 weeks later, using intravenous myocardial contrast echocardiography. Left ventricular ejection fraction (LVEF), LV regional wall motion (LVRWM), and LV end-diastolic volume index (LVEDVI) were measured 6 months later. RESULTS Baseline patient characteristics of the two groups were similar, including TIMI risk scores. Significant STR (> or =50% resolution compared to baseline) (66% versus 50%; Group 1 versus Group 2, p=0.02), no-reflow ratio (24% versus 34%, indicated by mean values, p=0.02), LVEF (61% versus 55%, p=0.0007), LVRWM (-1.56 versus -2.05, using the SD/chord, p=0.0001), and LVEDVI (60 ml/m(2) versus 71 ml/m(2), p=0.0007) were significantly better in Group 1, and the no-reflow ratio, LVEF, LVRWM and LVEDVI were significantly better in ATP-administered patients, regardless of antecedent angina or advanced age. ATP Administration was consistently identified as a significant determinant for STR, no-reflow ratio, LVEF, LVRWM, and LVEDVI. CONCLUSIONS Intravenous ATP administration during reperfusion is an independent determinant of STR and the no-reflow ratio, and LVEF, LVRWM, and LVEDVI at 6 months after primary PCI.

Clinical usefulness of drug-eluting stents in the treatment of dialysis patients with coronary artery disease

AIMS To investigate the clinical outcomes of paclitaxel-eluting stents (PES) and sirolimus-eluting stents (SES) in patients on dialysis. METHODS AND RESULTS Between May 2004 and December 2008, 95 patients on dialysis with 124 lesions were treated with PES alone, and were compared to 184 patients on dialysis with 244 lesions treated with SES alone, retrospectively. One-year major adverse cardiac event (MACE) including stent thrombosis, target lesion revascularisation (TLR), myocardial infarction (MI) and cardiac death were compared. Baseline characteristics were similar except for previous CABG (p = 0.02) and reference vessel diameter (p = 0.04). During hospitalisation, all cause death was more frequently observed in the PES group (p = 0.004). In-hospital MACE was not significantly different (p = 0.8). The incidence of 1-year MACE in the PES group was lower than that in the SES group (14.7%, 28.3%, p = 0.04), mainly due to the reduction of TLR (11.6%, 25.0%, p = 0.03). Rates of stent thrombosis (0%, 2.7%, p = 0.1), MI (1.1%, 3.8%, p = 0.2), and cardiac death (3.2%, 4.4%, p = 0.6) were not significantly different. CONCLUSIONS PES appears to be more efficient in reducing angiographic and clinical restenosis in dialysis patients compared with SES.

Role of transthoracic left atrial appendage wall motion velocity in patients with persistent atrial fibrillation and a low CHADS2 score

BACKGROUND AND PURPOSE Thromboembolic risk has been examined by semi-invasive transesophageal echocardiography. We assessed the risk of thrombogenesis in patients with persistent atrial fibrillation (AF) noninvasively by using transthoracic tissue Doppler echocardiography (TDE) in relation to a low CHADS2 score. METHODS Eighty patients with persistent AF underwent both transthoracic and transesophageal echocardiography. Peak left atrial appendage (LAA), wall motion velocity (WV) during LAA contraction was measured by transthoracic and transesophageal TDE. LAA flow velocity was also determined by transesophageal echocardiography. RESULTS Transthoracic LAAWV could be measured in 78 of the 80 patients, and the values were closely correlated with transesophageal TDE values (r=0.98) and with transesophageal LAA flow velocity (r=0.82). Transthoracic LAAWV was significantly lower with increasing spontaneous echo contrast (SEC) severity (severe SEC, mild SEC, no SEC: 5.7±2.4, 10.2±3.3, and 14.5±5.5cm/s, respectively). Severe SEC was noted in 31 of 61 patients with a CHADS2 score ≤2, in 19 of 46 patients with a CHADS2 score ≤1 and in 6 of 21 patients with a CHADS2 score=0. For diagnosing severe SEC, a transthoracic LAAWV <10cm/s had a sensitivity of 81% and specificity of 92% in the patients with a CHADS2 score ≤2, a sensitivity of 74% and specificity of 91% in the patients with a CHADS2 score ≤1 and a sensitivity of 44% and specificity of 83% in the patients with a CHADS2 score=0. CONCLUSIONS A transthoracic LAAWV <10cm/s in persistent AF patients with a low CHADS2 score may be a very specific diagnostic tool for evaluating severe SEC, one of the high risk factors for thromboembolism.

Intravenous administration of adenosine triphosphate disodium during primary percutaneous coronary intervention attenuates the transient rapid improvement of myocardial wall motion, not myocardial stunning, shortly after recanalization in acute anterior myocardial infarction.

BACKGROUND AND PURPOSE Administration of adenosine attenuates myocardial stunning after reperfusion in a canine experimental ischemic model. However, it is unknown whether administration of adenosine triphosphate disodium (ATP) during reperfusion can attenuate myocardial stunning after coronary recanalization in patients with acute myocardial infarction (MI). Therefore, we sought to elucidate the effects of ATP administration on serial changes of left ventricular systolic function before and after coronary recanalization. METHODS In 27 patients with first ST-elevation acute anterior MI, in whom primary percutaneous coronary intervention (PCI) was completed within 10 h after symptom onset, ATP at a mean rate of 103 microg/kg/min (n=16) or normal saline (n=11) was intravenously administered for 1 h during reperfusion. Left ventricular regional wall motion within the initially severely ischemic region was serially analyzed using the standard wall motion score index (WMSI) by transthoracic echocardiography. RESULTS Means of WMSIs were similar shortly before primary PCI in both groups (2.79 in ATP group and 2.69 in controls). They changed to 2.56 and 2.22 shortly after PCI, 2.49 and 2.39 on day 2, 2.34 and 2.30 on day 3, 2.19 and 2.25 on day 10, and 1.85 and 2.02, 6 months later, respectively. Transient improved regional wall motion within the initially severely ischemic region was observed shortly after PCI in controls (10.3% of observed segments); however, it was significantly suppressed in the ATP group (2.55%). The percent recovery of WMSI on day 10, which was defined as WMSI on day 10 normalized by improvement of WMSI for 6 months, was 63.8% in ATP group and 65.7% in controls, implying ATP administration could not reduce myocardial stunning by day 10 after primary PCI. CONCLUSIONS The high-dose administration of ATP during primary PCI prevented transient improved wall motion shortly after coronary recanalization rather than preventing left ventricular stunning. These results suggest that ATP can prevent reperfusion injury during primary PCI.

Vasomotility and Nitric Oxide Bioactivity of the Bridging Segments of the Left Anterior Descending Coronary Artery

We compared bridging and nonbridging coronary artery segments with respect to the vasoconstrictor effect of acetylcholine. Bridging segments were hypersensitive to the constrictor effect of acetylcholine, and results suggest that the effect of nitric oxide on the acetylcholine-stimulated condition is decreased, or that the smooth muscle sensitivity to acetylcholine is increased.

A case of acute coronary syndrome caused by extrinsic compression of the left main coronary artery due to pulmonary hypertension

Stenosis of the left main coronary artery (LMCA) due to extrinsic compression, producing symptoms of myocardial ischemia, is called left main compression syndrome. We report on a 43-year-old male with acute coronary syndrome who developed left main compression syndrome while waiting for a lung transplantation secondary to interstitial pneumonia, but underwent successful LMCA stenting as emergent treatment. Coronary angiography 3 months after the operation showed good stent patency in the LMCA, and the clinical course was favorable.

Coronary Sinus Morphology in Patients with Posteroseptal Atrioventricular Accessory Pathways

Background: There have been numerous reports about coronary sinus (CS) anomalies related to posteroseptal accessory pathways (APs). The purpose of this study was to explore the diameter and morphology of CS in patients with posteroseptal APs.