739SERCA2 Cys674 modification lead to ventricular arrhythmia due to impaired sarcoplasmic reticulum Ca2+ handling

Background

Sarcoplasmic reticulum Ca2+-ATPase2 (SERCA2) plays an important role in intracellular Ca2+ handling. Under pathological conditions, oxidative stress leads to irreversible oxidation of Cys674 on SERCA2 which causes intracellular Ca2+ overload. Intracellular Ca2+ overload is known as the cause of ventricular arrhythmia, but the relation between SERCA2 function and ventricular arrhythmia remains unclear.

Purpose

To investigate the role of Cys674 on SERCA2 in the intracellular Ca2+ handling and the induction of ventricular arrhythmia.

Methods

We employed SERCA2 Cys674Ser heterozygote knock-in mice (SKI) which mimics oxidative modification of Cys674 on SERCA2. Continuous infusion of angiotensin (ANG) (3mg/kg/day) or distilled water were performed both in wild type mice (WT) and SKI for a week. After 1 week, electrophysiological study and intracellular Ca2+ transient measurement were performed.

Results

ANG elevated blood pressure and represented cardiac hypertrophy with fibrosis similarly both in WT and SKI. The mRNA expression of calcium/calmodulin-dependent protein kinase-II (CaMKII), ryanodine receptor (RyR) and sodium-calcium exchanger (NCX) was increased in SKI heart compared with WT. QTc interval was prolonged in SKI compared with WT, which was markedly prolonged with ANG infusion. Under programmed electrical stimulation, only SKI with ANG showed high incidence of pacing induced ventricular arrhythmia (0/11 in WT/SKI control, 0/14 in WT with ANG vs. 8/14 in SKI with ANG, P < 0.01). In Ca2+ transient measurement, the peak Ca2+ transient amplitude (F/F0) was decreased (WT: 1.81 vs. SKI: 1.46, P < 0.01) and the time to 50% of cytosolic Ca2+ extrusion (T50) was prolonged (WT: 152.6ms vs. SKI: 202.3ms, P < 0.05) in SKI with ANG, suggesting decreased sarcoplasmic reticulum Ca2+ content and impaired SERCA2 activity in SKI with ANG. Intraperitoneal administration of dantrolene sodium (DAN) which inhibit Ca2+ leakage from RyR receptor normalized decreased F/F0 and prolonged T50 in SKI with ANG (Fig. 1 A, B). DAN also prevented QTc prolongation and decreased the incidence of ventricular arrhythmia in SKI with ANG (8/14 in SKI with ANG vs. 2/13 in SKI with ANG + DAN, P < 0.05) (Fig. 2).

Conclusions

The loss of thiol on Cys674 under pathological condition resulted in impaired Ca2+ handling and high incidence of ventricular arrhythmia which were ameliorated by inhibition of Ca2+ leakage through RyR. Oxidative modification of Cys674 on SERCA2 might contribute to Ca2+ mishandling and arrhythmogenesis.

Abstract Figure.

Anti-sympathetic action enhances statin's pleiotropic effects: the combined effect of rosuvastatin and atenolol on endothelial function

AIM

Assessment of flow-mediated dilation (FMD) and nitroglycerin-mediated dilation (NMD) in the brachial artery by a new device (UNEXEF18G) has been reported to be excellent for evaluating endothelial function, and sympathetic overdrive can accelerate the atherosclerotic process. The purpose of this study was to investigate and confirm whether anti-sympathetic beta-blocking action can enhance the pleiotropic effects of statins.

METHODS

FMD and NMD were measured using the UNEXEF18G before and after 4-week treatment of rosuvastatin (5 mg/day) with or without atenolol (25 mg/day) in 44 hypercholesterolemic patients (70±8 years old, LDL-C >140 mg/dL) with hypertension. Patients were randomly allocated to two treatment arms: rosuvastatin alone (R-group, N.=22) and rosuvastatin with atenolol (RA-group, N.=22).

RESULTS

Baseline FMD was not different between the two treatment arms, and both groups showed improvement in FMD (R-group, 3.48±1.9% to 4.65±2.41%, P<0.05; RA-group, 3.42±1.48% to 5.46±1.79%, P<0.05), while there were no differences in NMD. The effects on lipid profiles were identical in the two groups. In addition, FMD improvement was greater in the RA-group than in the R-group (Δchange 2.15±1.29% vs. 1.16±1.15%, P<0.05).

CONCLUSION

Beta-blockade enhances the pleiotropic effects of statins on endothelial function. The mechanism should be confirmed by further studies.

Thrombus-targeted perfluorocarbon-containing liposomal bubbles for enhancement of ultrasonic thrombolysis: in vitro and in vivo study

BACKGROUND

External low-frequency ultrasound (USD) in combination with microbubbles has been reported to recanalize thrombotically occluded arteries in animal models.

OBJECTIVE

The purpose of this study was to examine the enhancing effect of thrombus-targeted bubble liposomes (BLs) developed for fresh thrombus imaging during ultrasonic thrombolysis.

METHODS

In vitro: after the administration of thrombus-targeted BLs or non-targeted BLs, the clot was exposed to low-frequency (27 kHz) USD for 5 min. In vivo: Rabbit iliofemoral arteries were thrombotically occluded, and an intravenous injection of either targeted BLs (n = 22) or non-targeted BLs (n = 22) was delivered. External low-frequency USD (low intensity, 1.4 W cm(-2) , to 12 arteries, and high intensity, 4.0 W cm(-2) , to 10 arteries, for both the targeted BL group and the non-targeted BL group) was applied to the thrombotically occluded arteries for 60 min. In another 10 rabbits, recombinant tissue-type plasminogen activator (rt-PA) was intravenously administered.

RESULTS

In vitro: the weight reduction rate of the clot with targeted BLs was significantly higher than that of the clot with non-targeted BLs. In vivo: TIMI grade 3 flow was present in a significantly higher number of rabbits with USD and targeted BLs than rabbits with USD and non-targeted BLs, or with rt-PA monotherapy. High-intensity USD exposure with targeted BLs achieved arterial recanalization in 90% of arteries, and the time to reperfusion was shorter than with rt-PA treatment (targeted BLs, 16.7 ± 5.0 min; rt-PA, 41.3 ± 14.4 min).

CONCLUSIONS

Thrombus-targeted BLs developed for USD thrombus imaging enhance ultrasonic disruption of thrombus both in vitro and in vivo.

Angioplasty decreases prolonged QT dispersion in patients with angina pectoris but not in patients with prior myocardial infarction

BACKGROUND AND HYPOTHESIS

Prolonged QT dispersion (QTd) is shortened by successful percutaneous transluminal coronary angioplasty (PTCA) in patients with ischemic heart disease. Particularly, QTd plays an important role in the prognostication in patients with prior myocardial infarction (MI). However, whether the effect of PTCA on QTd differs in patients with and without prior MI is not clear, and this study sought to clarify this question.

METHODS

In 41 consecutive patients with ischemic heart disease, we measured QTd from a routine 12-lead electrocardiogram taken at 72 h before and after successful PTCA. Patients were divided into two groups based on the presence or absence of prior MI: Group 1 consisted of 24 patients with angina (61 +/- 11 years old) without prior MI and Group 2 was comprised of 17 patients (69 +/- 10 years old) with prior MI. QTd was calculated as the difference between the maximum and minimum QT and QT corrected for heart rate (QTc), using Bazett's formula for calculating QTcd. All measurements were obtained manually and blindly.

RESULTS

In Group 1, 15 of 24 patients (63%) demonstrated multivessel disease and 16 of 24 (67%) patients had high QTd > 60 ms. Percutaneous transluminal coronary angioplasty decreased QTd and QTcd in Group 1 (QTd, from 83 +/- 35 to 57 +/- 19 ms, p < 0.05 ; QTcd, from 89 +/- 37 to 63 +/- 33 ms, p < 0.05), whereas no changes were observed in Group 2 (QTd, from 73 +/- 25 to 69 +/- 22 ms, NS; QTcd, from 80 +/- 30 to 79 +/- 28 ms, NS). QTd is more sensitive to decrease by successful PTCA in patients with angina than in patients with prior MI.

CONCLUSIONS

The effect of successful PTCA on inhomogeneity of ventricular repolarization reflected by QTd in patients with prior MI is different from that in patients without prior MI.

Effect of aprindine on heart rate variability indices in patients with ischemic heart disease

BACKGROUND

Decreased heart rate variability indices (HRV) are associated with untoward outcome of patients with ischemic heart disease (IHD). Most class I antiarrhythmic agents decrease HRV, but aprindine (a new class I antiarrhythmic agent) is reported to increase HRV in patients without ischemia.

HYPOTHESIS

The study was undertaken to determine whether apridine might increase HRV in patients with IHD.

METHODS

To investigate the effect of aprindine on HRV in patients with IHD, we performed 24-h ambulatory electrocardiogram (ECG) at the end of placebo and aprindine (60 mg daily) treatment phases on 38 patients with IHD and at least isolated premature ventricular contractions (PVC). The study protocol utilized a single blind, 4-week, placebo-controlled design. Heart rate variability from ambulatory ECG included SDNN (ms), SDANN (ms), SD (ms), rMSSD (ms), pNN50 (%); frequency analysis of HRV consisting of total (ms, 0.01-1.00 Hz), low (ms, 0.04-0.15 Hz), and high (ms, 0.15-0.40 Hz) components.

RESULTS

Study patients were divided into three groups according to the severity of IHD and antiarrhythmic efficacy of aprindine. Group 1 consisted of 15 patients with angina with single-vessel disease, and Group 2 was composed of 10 patients with either multivessel disease or post myocardial infarction; PVCs decreased in both groups as result of aprindine treatment. Group 3 consisted of 13 patients who showed no decreased PVC after aprindine treatment. RMSSD increased, and pNN50 and high-frequency spectra tended to increase in Group 1, while SD, rMSSD, pNN50, and total and low-frequency spectra decreased in Group 3; no significant changes were observed in Group 2. Aprindine significantly augments vagal activity, as reflected by the increase of rMSSD, pNN50, and high-frequency spectra in mild IHD.

CONCLUSION

These salutary effects are less in more severe IHD, but aprindine does not aggravate HRV. Thus, if there are salutary effects on arrhythmias and no proarrhythmic effects, aprindine could be prescribed to patients with IHD without concern about decreasing HRV.

Morning attenuation of endothelium-dependent, flow-mediated dilation in healthy young men: possible connection to morning peak of cardiac events?

BACKGROUND AND HYPOTHESIS

Brachial artery flow-mediated dilation (FMD), a noninvasive, widely used clinical index of endothelial function and magnitude of FMD, has been reported to be closely related to many coronary risk factors and coronary atherosclerosis. However, there has been no study that examines the diurnal change of FMD. We designed this study to reveal the diurnal variation of FMD in healthy volunteers.

METHODS

We examined FMD in response to reactive hyperemia by high resolution ultrasound in 13 healthy young men (age 25-32) at four different times over the course of a day.

RESULTS

Mean measures of brachial artery FMD was 4.0% at 8:00, 5.3% at 12:00, 9.7% at 17:00, and 6.9% at 21:00 hours. Flow-mediated dilation at 8:00 and at 12:00 hours was significantly lower than that at 17:00 (p < 0.05).

CONCLUSIONS

These results show that endothelial function has diurnal variation and is significantly attenuated in the morning. Morning attenuation of endothelial function should be recognized in clinical research and may play an important role in the circadian variation of the occurrence of acute cardiovascular events.

Endothelial dysfunction and decreased exercise tolerance in interferon-alpha therapy in chronic hepatitis C: relation between exercise hyperemia and endothelial function

BACKGROUND

We previously reported that reversible endothelial dysfunction is caused by interferon-alpha therapy (IFN) in patients with chronic hepatitis C. In experimental studies, limb blood flow during exercise is reported to be dependent on endothelium-derived nitric oxide.

HYPOTHESIS

The purpose of this study was to confirm the effect of IFN on endothelial function and to investigate whether exercise hyperemia is dependent on endothelial function in humans.

METHODS

We performed symptom-limited exercise treadmill testing and measured flow-mediated vasodilation (FMD, endothelium-dependent vasodilation) and sublingual glyceryl-trinitrate-induced dilation (GTN-D, 0.3 mg, endothelium-independent vasodilation) in the brachial artery by using high-resolution ultrasound in 10 patients with chronic active hepatitis C (age 53 +/- 11 years, 2 men, 8 women) before and immediately after administration of recombinant interferon 2b (10 million U/day) for 4 weeks.

RESULTS

There were no significant abnormal findings in any patients in routine studies of 24-h ambulatory electrocardiogram monitoring, two-dimensional echocardiography, and exercise treadmill testing both before and after treatment. Leg fatigue and exhaustion were the reasons for termination of exercise treadmill testing in each patient. Pressure rate product was calculated at rest and peak exercise. Interferon-alpha therapy significantly (p<0.05) decreased FMD (6.8 +/- 3.1 vs. 1.9 +/- 2.6%), exercise treadmill testing tolerance time (437 +/- 89 vs. 395 +/- 62 s) and peak pressure rate product (283 +/- 41 vs. 241 +/- 47 mmHg x beats/min x 10(-2)), but not GTN-D (13.4 +/- 5.4 vs. 17.0 +/- 5.5%). The change of FMD due to IFN significantly and highly correlated with exercise treadmill testing tolerance time (r = 0.86, p<0.001), but not with change of peak pressure rate product, suggesting that FMD is more closely related to the condition of the peripheral circulation than is cardiac performance.

CONCLUSION

These results suggest that IFN in patients with chronic hepatitis C impairs endothelial function and exercise tolerance, and that endothelial function might be at least partly involved in exercise hyperemia in humans.

Significance of circulatory epinephrine levels in exercise-induced neurally mediated syncope

BACKGROUND AND HYPOTHESIS

Previous research has failed to document temporal changes in epinephrine levels in patients with neurally mediated syncope associated with exercise. The purpose of this study was to investigate the role of circulatory catecholamines in exercise-induced neurally mediated syncope, specifically focusing on epinephrine levels.

METHODS

The present study deals with temporal changes of circulatory catecholamine levels during head-up tilt tests (40 min, 80 degree tilt) in 62 patients with syncope of unknown origin, 7 of whom had syncope associated with exercise (exercise-induced group, 19+/-3 years). Data were compared with 10 control subjects (control group, 45+/-23 years). Of the 55 patients with syncope not associated with exercise, 32 tested positive for the head-up tilt tests (positive group, 31+/-16 years) and 23 patients tested negative (negative group, 46+/-19 years). Blood samples for circulatory catecholamine assay were obtained from the antecubital vein in the baseline supine position 2 min after the tilt started, every 10 min during tilt, and at the time of the onset of symptoms or the end of tilt. Levels of norepinephrine and epinephrine were determined using the high-pressure liquid chromatography (HPLC) method (pg/ml).

RESULTS

Plasma norepinephrine levels among the four groups were similar at the supine position and during tilt testing. In contrast, patients in the exercise-induced group had significantly higher maximum epinephrine levels during head-up tilt testing than the other three groups (288+/-191 vs. 148+/-117, 66+/-31, and 54+/-27 pg/ml, respectively, p < 0.05). Patients in the positive group had higher maximum epinephrine levels than those in the negative group (p <0.05). Also, patients in the exercise-induced group and those in the positive group had a significantly shorter tilt-testing time than patients in the negative and control groups.

CONCLUSIONS

A marked increase of epinephrine was observed during head-up tilt testing in patients with neurally mediated syncope associated with exercise. The present findings further accelerate the identification of the role of epinephrine in the mechanisms behind neurally mediated syncope associated with exercise.

Endothelial function and peripheral vasomotion in the brachial artery in neurally mediated syncope

BACKGROUND

Paradoxical peripheral vasodilation is one of the suspected mechanisms of neurally mediated syncope. Parasympathetic stimulation following sympathetic activation during orthostatic stress mainly contributes to this vasodilation.

HYPOTHESIS

Since endothelial function modulates peripheral vascular tone, this study aimed to determine whether endothelial function and inappropriate peripheral vasomotion has a significant role in the pathogenesis of neurally mediated syncope.

METHODS

To investigate whether endothelial function is augmented or whether abnormal peripheral vasomotion exits, flow-mediated dilation (FMD, endothelium-dependent vasodilation) and sublingual glyceryl trinitrate-induced dilation (0.3 mg, GTN-D, endothelium-independent vasodilation) were measured in the brachial artery in 16 patients with neurally mediated syncope, aged 33 +/- 10 years, by using high-resolution ultrasound. All patients underwent positive head-up tilt testing. These measures were compared with those in 16 control subjects matched with the patients by age, gender, and coronary risk factors. For FMD, percent diameter changes were obtained from baseline to hyperemic conditions (1 min after 5 min occlusion of the forearm artery). There were five smokers in both the patient and the control groups, but there was no structural heart disease in either group.

RESULTS

Baseline brachial artery diameters were comparable (3.8 +/- 0.6 vs. 3.8 +/- 0.7 mm, NS). Flow-mediated dilation in patients with neurally mediated syncope had a normal value of 9.8 +/- 5.0% despite the inclusion of five smokers. Flow-mediated dilation and GTN-D in patients with neurally mediated syncope were significantly greater than those in controls (9.0 +/- 5.0 vs. 3.0 +/- 3.5%, p<0.05; 18.4 +/- 5.5 vs. 14.1 +/- 4.4%, p<0.05).

CONCLUSIONS

Augmented endothelial function and/or abnormal peripheral vasomotion in peripheral arteries are important in patients with neurally mediated syncope in selected populations.

Autonomic responses to orthostatic stress in head-up tilt testing: relationship to test-induced prolonged asystole

BACKGROUND

Prolonged asystole is sometimes an extreme manifestation of neurally mediated syncope.

HYPOTHESIS

To investigate the mechanism of head-up tilt testing-induced prolonged (life-threatening) cardiac asystole, we measured temporal changes in frequency domain heart rate variability indices in 25 patients with syncope of undetermined etiology.

METHODS

Head-up tilt testing (80 degrees) was performed in 25 patients for up to 40 min or until asystole or syncope occurred. Three patients (Group 1; 37 +/- 13 years, 1 man 2 women) had an episode of prolonged cardiac asystole (> or = 10 s) during testing, necessitating cardiopulmonary resuscitation. Syncope, but no asystole, was induced in 10 patients (Group 2; 48 +/- 31 years, 6 men, 4 women), and 12 patients (Group 3; 55 +/- 20 years, 5 men, 7 women) failed to show asystole or syncope during testing. Power spectra of low (0.04-0.15 Hz) and high (0.15-0.40 Hz) frequency, and total (0.01-1.00 Hz) frequency spectra were measured in consecutive 2 min segments throughout the test.

RESULTS

Maximally changed values in heart rate, systolic blood pressure, and heart rate variability indices during testing were compared among the three groups (maximally changed values did not include the values during tilt-induced symptoms). High frequency spectra in Groups 2 and 3, but not in Group 1, decreased during the test. High frequency spectra, low frequency spectra, and total spectra in Group 1 were significantly higher than those in Groups 2 and 3 during testing. In Group 1 patients, findings at test-induced asystole were consistent with exaggerated sympathetic and concurrent persistent parasympathetic activity.

CONCLUSION

Unusual autonomic responses to orthostatic stress can cause prolonged asystole, and this autonomic nerve dysregulation may relate to asystolic episodes associated with cardiovascular collapse.

Frequency domain heart rate variability and plasma norepinephrine level in the coronary sinus during handgrip exercise

BACKGROUND

Heart rate (HR) variability has been recognized as an important noninvasive index of autonomic nervous activities. However, the relationship between HR variability and cardiac circulating norepinephrine (NE), especially with respect to coronary ischemia, remains unclear.

HYPOTHESIS

This study was undertaken to determine whether HR variability indices can reflect cardiac NE levels during handgrip exercise.

METHODS

We simultaneously measured HR variability and cardiac NE overflow rate in 32 patients (30 men, 2 women) during a 6-min isometric handgrip exercise. Among the 32 subjects, 20 (19 men, 1 woman) had coronary artery disease (CAD) and 12 (control group; 11 men, 1 woman) did not.

RESULTS

Hemodynamics and cardiac NE overflow rates among subjects at rest were not significantly different between the two groups. In the normal subjects, low-frequency (LF) spectra and LF/HF (high-frequency) ratios were not significantly changed during handgrip exercise, but HF spectra significantly increased from 10.1 +/- 4.5 to 12.2 +/- 7.0 ms (p < 0.05). In the subjects with CAD, LF and LF/HF spectra were significantly (p < 0.05 and 0.01, respectively) increased by handgrip exercise. High-frequency spectra were not significantly changed by handgrip exercise. In the normal subjects, a significant negative relation (r = -0.76, p < 0.01) was obtained between HF change and cardiac NE overflow rate, whereas this relationship was not significant in the subjects with CAD. The correlation between changes of LF/HF and cardiac NE overflow rate was significant in the normal (r = 0.56, p < 0.05) but not in subjects with CAD.

CONCLUSION

These results suggest that vagal modulation of HR variability is more prominent in normal coronary artery subjects than in CAD subjects during handgrip exercise. Heart rate variability indices may thus serve as adequate indicators of autonomic nerve activity in subjects with normal coronary arteries but not in those with CAD, probably due to decreased adaptation to physical stress during handgrip exercise.

Non-invasive estimation of arterial blood pH using exhaled CO/CO2 analyser, microwave radar and infrared thermography for patients after massive haemorrhage

In order to conduct non-contact estimation of arterial blood pH after massive haemorrhage, we calculated the arterial pH based on linear-regression analysis of exhaled gas concentrations (CO and CO2) and vital signs (heart rate, respiratory rate, and surface temperature) measured using non-contact methods in hypovolemic animals.

Recombinant interferon alpha treatment decreases heart rate variability indices and impairs exercise tolerance in patients with chronic hepatitis

Complications of interferon (IFN) therapy include cardiac arrhythmias, impaired cardiac function and myocardial ischemia. Decreased heart rate variability (HRV) indices, impaired exercise tolerance and decreased left ventricular (LV) function are related to unfavorable outcome of heart disease. To investigate the effect of IFN therapy on HRV, exercise tolerance and cardiac function, 24-h ambulatory electrocardiographic monitoring (AECG), two-dimensional echocardiography, and exercise treadmill testing (ETT) was performed in 9 patients (age 56 +/- 9 years-old) with chronic hepatitis and without underlying heart disease before and after treatment with IFN (recombinant alpha 2b; 10 x 10(6) U/day for 4 weeks). HRV parameters consisted of standard deviation of RR interval (sdNN, ms), SDANN (ms), S.D. index (ms), rMSSD (ms), pNN50 (%) and frequency analysis of heart rate spectrum resulted in low (ms, 0.04-0.15 Hz), high (ms, 0.15-0.40 Hz) and total (ms, 0.01-1.00 Hz) frequency components. Ischemia was not detected by AECG or ETT, and LV function was normal after INF treatment in all patients. However, INF treatment resulted in a decrease in exercise tolerance time (449 +/- 94 s vs. 329 +/- 67 s, P < 0.05) and a decrease in several HRV parameters (S.D. index, 42 +/- 5 ms vs. 37 +/- 9 ms; rMSSD, 22 +/- 5 ms vs. 19 +/- 4 ms; pNN50, 4 +/- 3% vs. 2 +/- 1%; P < 0.05). Further, patients treated with INF tended to have a lower sdNN and total frequency spectra, although this difference did not reach the level of statistical significance. These data suggest that the arrhythmogenic effect of INF may be mediated by decreases in HRV and impairment of exercise tolerance even in patients without overt heart diseases. Further, INF therapy may be contraindicated in patients with predisposing severe cardiac disorders, including arrhythmias, ischemia and decreased LV function.

A novel apparatus for non-contact measurement of heart rate variability: a system to prevent secondary exposure of medical personnel to toxic materials under biochemical hazard conditions, in monitoring sepsis or in predicting multiple organ dysfunction syndrome

BACKGROUND

The impaired balance of the low-frequency/high-frequency ratio obtained from spectral components of RR intervals can be a diagnostic test for sepsis. In addition, it is known that a reduction of heart rate variability (HRV) is useful in identifying septic patients at risk of the development of multiple organ dysfunction syndrome (MODS). We have reported a non-contact method using a microwave radar to monitor the heart and respiratory rates of a healthy person placed inside an isolator or of experimental animals exposed to toxic materials.

APPARATUS DESIGN AND TESTING

With the purpose of preventing secondary exposure of medical personnel to toxic materials under biochemical hazard conditions, we designed a novel apparatus for non-contact measurement of HRV using a 1215 MHz microwave radar, a high-pass filter, and a personal computer. The microwave radar monitors only the small reflected waves from the subject's chest wall, which are modulated by the cardiac and respiratory motion. The high-pass filter enhances the cardiac signal and attenuates the respiratory signal. In a human trial, RR intervals derived from the non-contact apparatus significantly correlated with those derived from ECG (r=0.98, P<0.0001). The non-contact apparatus showed a similar power spectrum of RR intervals to that of ECG.

CONCLUSIONS

Our non-contact HRV measurement apparatus appears promising for future pre-hospital monitoring of septic patients or for predicting MODS patients, inside isolators or in the field for mass casualties under biochemical hazard circumstances.

Effect of betaxolol hydrochloride on heart rate variability indices during exercise stress testing in patients with hypertension

Betaxolol hydrochloride is a beta1-selective antagonist that produces vasodilation in patients with hypertension and ischemic heart disease. The goal of the present study was to characterize the effect of betaxolol on heart rate variability indices (HRV), a well-established prognostic marker. Symptom limited-treadmill exercise testing was performed in 17 hypertensive patients (60.9 +/- 14.8 years-old) before and immediately a 3 weeks course of betaxolol hydrochloride (5 mg daily). Frequency domain HRV (high frequency spectra, HF; 0.15-0.40 Hz: low frequency spectra, LF; 0.04-0.15 Hz) was measured during exercise treadmill testing using MemCalc software. Betaxolol hydrochloride significantly decreased the maximal systolic blood pressure and heart rate (184 +/- 29 vs. 156 +/- 26 mmHg, P < 0.01; 132 +/- 21 vs. 113 +/- 15 bpm, P < 0.01) and significantly increased HF and LF during exercise treadmill testing (HF, 32 +/- 36 vs. 56 +/- 55 men/Hz, P < 0.01; LF, 64 +/- 58 vs. 95 +/- 86 men/Hz, P < 0.01). Thus, treatment with betaxolol hydrochloride resulted in a decrease in blood pressure during exercise treadmill testing and in an increase in HRV. This suggests that this agent could have beneficial effects on long-term prognosis in patients with hypertension.

Effect of antiarrhythmic agents on heart rate variability indices after myocardial infarction: comparative experimental study of aprindine and procainamide

The cardiac arrhythmic suppression trial (CAST) reported that antiarrhythmic treatments in post-myocardial infarction (MI) patients resulted in poor outcome and decreased in heart rate variability indices (HRV). The goal of the present study was to determine whether aprindine and procainamide, antiarrhythmic agents that increase HRV, result in beneficial effects in post-MI rabbits. Four weeks before experiment, MI was induced in four rabbits by ligating the major branch of left coronary artery. A total of eight rabbits (four post-MI and four normal rabbits) were randomly assigned to treatment with either intravenous aprindine (1 mg/kg) or intravenous procainamide (15 mg/kg). Frequency domain HRV (low frequency spectra, LF, 0.04-0.15 Hz; high frequency spectra, HF, 0.15-0.40 Hz) were assessed by MemCalc software. Aprindine significantly increased HF and LF in both MI and normal rabbits, whereas procainamide tended to decrease HF and LF in MI and normal rabbits (in total rabbits; aprindine, LF, from 6.3 +/- 7.9 to 16.5 +/- 15.0 ms(2)/Hz, P < 0.05; HF, from 8.0 +/- 11.7 to 17.5 +/- 15.0 ms(2)/Hz, P < 0.05; procainamide, LF, from 4.9 +/- 7.4 to 4.8 +/- 8.5 ms(2)/Hz, NS; HF, from 11.1 +/- 23.0 to 5.1 +/- 10.6 ms(2)/Hz, NS). Under pharmacological denervation with propranolol (0.1 mg/kg) and atropine (0.04 mg/kg), aprindine increased LF and HF (LF, from 0.2 +/- 0.2 to 0.8 +/- 0.7 ms(2)/Hz, P < 0.05; HF, from 0.1 +/- 0.0 to 0.2 +/- 0.0 ms(2)/Hz, P < 0.05). These data suggest that aprindine can increase HRV in post-MI rabbits. Further experiments in human subjects would be of benefit.

Non-contact determination of vital sign alterations in hypovolaemic states induced by massive haemorrhage: an experimental attempt to monitor the condition of injured persons behind barriers or under disaster rubble

To assess a non-contact method to determine the physical alteration of human subjects confined behind a barrier or under disaster rubble, an experimental, non-contact monitoring system was tested on rabbits in a hypovolaemic state. New Zealand male rabbits behind a barrier were subjected to hypovolaemic shock induced by the withdrawal of arterial blood (2ml per 100g body weight). The hypovolaemic state was determined by linear discriminant analysis using non-contact-derived variables: heart rate X1 and respiratory rate X2. Sixteen rabbits were equally divided between the hypovolaemic and control groups. To obtain the heart and respiratory rates simultaneously, the fast Fourier transform (FFT) was performed on the 1215MHz microwave radar analogue output. The linear discriminant function calculated by non-contact-derived variables was negative in the eight hypovolaemic rabbits and positive in the eight controls, so that the linear discriminant function could distinguish the hypovolaemic group from the control group. The Mahalanobis D-square (an index for classification accuracy) was 5908; the classification error rate corresponding to this value was small and negligible. The hypovolaemic rabbits developed metabolic acidosis (HCO3- 18.6+/-11.1 mmol l(-1) and pH 7.15+/-0.18 in arterial blood). The systolic blood pressure of the hypovolaemic group and the control was 56+/-4 and 83+/-6 mmHg, respectively (p < 0.01). The proposed method appears promising for applications to monitor the condition of human subjects behind barriers or under disaster rubble.

Flow-mediated dilation in brachial artery in the second half of pregnancy and prediction of pre-eclampsia

Endothelial injury and increased vascular reactivity are involved in the pathogenesis of pre-eclampsia (pregnancy-induced hypertension). To investigate whether flow-mediated dilation (endothelium-dependent dilation) and the reactive hyperemic response can predict pre-eclampsia, we prospectively measured flow-mediated dilation and the Doppler flow velocity pattern (V, cm/s) in the brachial artery using high-resolution ultrasound in 43 pregnant women (32+/-5 years old) in the second half of their pregnancy, and compared the findings with traditional risk factors. Regarding the Doppler flow velocity pattern, the pulsatility index (PI)=(systolic V-diastolic V)/mean V and resistance index (RI)=(systolic V-diastolic V)/systolic V were calculated. For the flow-mediated dilation, the per cent diameter changes were determined based on those from baseline to hyperemic conditions. Nine women suffered from pre-eclampsia and 34 women remained normotensive. Only flow-mediated dilation was found to be significantly lower in the subsequently developed pre-eclampsia patients (1.6+/-1.0% in subsequently developed pre-eclampsia patients vs 11.0+/-4.5% in normotensive patients, P<0.05). Neither the other traditional factors nor the Doppler flow velocity pattern were significantly different between the subsequently developed pre-eclampsia and normotensive patients. If a normal cutoff value of 3.0% obtained from age-matched 14 nonpregnant women (32+/-7 years old) in our laboratory was used, the positive predictive value of flow-mediated dilation (<3.0%) for subsequent pre-eclampsia is 90% and the negative predictive value is 100%. In conclusion, flow-mediated dilation in brachial artery can be a simple and noninvasive modality to predict pre-eclampsia.

Development of a continuous temperature mapping system using a deep body thermometer

To determine continuous body temperature distribution, an inexpensive temperature mapping system was developed using a deep body thermometer adopting the finite-element method. A stripe with 16 thermocouples was wrapped around the waist of rats to measure body surface temperatures (the boundary conditions). The abdominal deep temperature of the rats was measured from the dorsum using the thermal compensation probe of a deep body thermometer. The abdominal temperature of the rats was mapped by solving a heat conduction equation using surface and deep temperatures obtained in real time. The temperature measured with a thermocouple inserted into the abdominal centre of the rats correlated well with the calculated temperature (r = 0.93, p < 0.01). The system is low cost and simple to use compared with the magnetic resonance temperature mapping system. Our temperature mapping system could potentially result in improved management of patients in critical care medicine.

The repeatability of left ventricular volume assessment by a new ambulatory radionuclide monitoring system during head-up tilt

The precise measurement of changes in left ventricular volume is important to elucidate the mechanisms of neurally mediated syncope. This study was conducted to determine whether or not a brand-new ambulatory radionuclide monitoring system (C-VEST system) can be clinically used to easily and precisely measure left ventricular volume and function in tilt testing. To assess the repeatability of the C-VEST system, 12 healthy volunteers (mean age 24+/-4 years old) underwent 20 minute head-up tilt testing and we measured the temporal changes in left ventricular volume and ejection fraction twice a day (first and second studies). To investigate the changes in the C-VEST measurements and the detector position in the first and second studies, tilt testing was performed with an 80-degree passive tilt, which is the same as the standard procedure used in diagnosing neurally mediated syncope. The coefficient of repeatability for both the C-VEST and detector position was well within the clinical range (coefficient of repeatability in left ventricular volume ranged from 1.7 to 2.8; coefficient of repeatability in the detector position ranged from 2.3 to 3.1). Precise evaluation of the left ventricular volume can be achieved by an ambulatory radionuclide monitoring system in tilt testing.

Assessment of left ventricular volume by an ambulatory radionuclide monitoring system during head-up tilt in patients with unexplained syncope: relation to autonomic activity assessed by heart rate variability

BACKGROUND

Decreased left ventricular volume during head-up tilt plays an important role in triggering syncope in patients with neurally mediated syncope. However, precise changes in left ventricular volume during head-up tilt have not been well investigated. This study was conducted to test the hypothesis that the decline in left ventricular volume during tilt could trigger ventricular mechanoreceptor activation.

METHODS AND RESULTS

To investigate the mechanisms of tilt-induced syncope, we measured the temporal changes in left ventricular volume, ejection fraction, cardiac output, and heart rate variability indices during head-up tilt in 25 patients with syncope of undetermined etiology. Eleven patients had a cardioinhibitory response (CI group), 7 patients showed a vasodepressor response (VD group), and 7 patients demonstrated a negative response (NG group). Before syncope, ejection fraction increased most in the CI group, the left ventricular end-diastolic volume declined most in the VD group (VD group, -11.0% +/- 3.3%; CI group, -2.8% +/- 4.8%; NG group, -3.4% +/- 2.2%; P <.005), and the high-frequency spectra increased most in the CI group (CI group, 25.0% +/- 21.0%; VD group, -4.1% +/- 11.7%; NG group, -5.3% +/- 12.7%; P <.01). The vasodepressor response was dependent on left ventricular volume, whereas the cardioinhibitory response was related to the vagal activity reflected by high-frequency spectra.

CONCLUSIONS

The precise evaluation of left ventricular volume by an ambulatory radionuclide monitoring system combined with a heart rate variability analysis is considered useful for clarifying the pathophysiology of neurally mediated syncope.

Determining the temperature distribution of swine aorta with simulated atheromatous plaque under pulsed laser irradiation: an experimental attempt to detect the vulnerability of atherosclerosis

We developed a method to determine the temperature distribution of swine aortas with simulated atheromatous plaques in order to measure the temperature of atherosclerotic lesions. The inflammation associated with temperature elevation is considered to be one of the aggravating mechanisms of atherosclerosis resulting in fissuring or rupture of atheromatous plaques. The temperature distribution of plaques covered by fibrous caps cannot be measured by conventional thermistors. Indocyanine green (ICG) solution was injected into the subintima of swine aorta to simulate the light absorption coefficient of human atheromatous plaques. The temperature distribution was calculated from measured temperature changes of the aortic intima under pulsed laser irradiation. The aorta was heated from the adventitial side with a halogen lamp to simulate the temperature elevation derived from inflammation. The temperature distribution of the aorta was obtained by solving the heat transfer equation using the surface layer thickness (corresponding to the fibrous cap thickness). The surface layer thickness can be calculated using the following working formula: D(microm)=1363-398DeltaTs+35DeltaTs(2), where AT, denotes intimal surface temperature change under pulsed laser irradiation. The calculated temperature of the ICG layer (corresponding to the atheromatous core) correlated well with the measured temperature (r=0. 97, p<0.0001).

Different mechanisms of isoproterenol-induced and nitroglycerin-induced syncope during head-up tilt in patients with unexplained syncope: important role of epinephrine in nitroglycerin-induced syncope

INTRODUCTION

A reduction in left ventricular volume and an increase in epinephrine levels have been reported in tilt-induced neurally mediated syncope. To compare the mechanisms of isoproterenol-induced and nitroglycerin-induced syncope during head-up tilt and to investigate the role of catecholamines, the temporal changes in plasma levels of norepinephrine and epinephrine and in left ventricular volume were measured.

METHODS AND RESULTS

The first study population consisted of 90 patients with syncope of unknown etiology and 12 control subjects. The second study population consisted of 43 patients with unexplained syncope. In the first study, head-up tilt (80 degree angle) was conducted for 40 minutes, and norepinephrine and epinephrine levels were measured. In the second study, all patients were randomly allocated to either isoproterenol test (20 patients) or nitroglycerin test (23 patients) for 20-minute head-up tilt. Isoproterenol infusion was given at a rate of 1 to 3 microg/min. Intravenous infusion of nitroglycerin was started at 250 microg/hour with increasing dosages up to 1,500 microg/hour. Norepinephrine and epinephrine were measured in peripheral venous blood. Left ventricular volumes were measured by echocardiography with patients in the supine position and during head-up tilt every 1 minute. End-diastolic volume and end-systolic volume were calculated. In the first study, 61 patients demonstrated a positive response and 29 patients demonstrated a negative response. Plasma norepinephrine changes during head-up tilt were not significantly different, whereas epinephrine levels were significantly higher in the positive patients than in the negative and control subjects (148 +/- 118 pg/mL vs 66 +/- 31 pg/mL and 55 +/- 27 pg/mL). Thirteen of the 20 patients given isoproterenol and 15 of the 23 patients given nitroglycerin showed a positive head-up tilt (65.0% vs 65.2%; P = NS). During isoproterenol and nitroglycerin infusion head-up tilt, epinephrine in the positive group determined by the nitroglycerin test was significantly higher than that in the other three groups (103 +/- 38 pg/mL vs 60 +/- 33 pg/mL, 31 +/- 21 pg/mL, and 50 +/- 52 pg/mL). In contrast, end-systolic volume was significantly smaller in the positive group than in the other three groups based on findings of the isoproterenol test.

CONCLUSION

The findings suggest that nitroglycerin triggers head-up tilt-induced syncope by increasing epinephrine levels, whereas isoproterenol induces syncope by decreasing left ventricular volume.

New thermo-couple copper constantan catheter for measuring regional coronary blood flow and evaluating metabolism

A new thermodilution catheter with a thermo-couple copper constantan and latex balloon in the tip has recently been developed. This device has two orifices. The left anterior descending (LAD) and/or left circumflex (LCX) flows were measured using a Doppler flow wire. The correlation between the LAD and GCV flow as well as between the LCX and CS-GCV flow were studied in closed chest animals. The flow distributions were evaluated by colored microspheres that were infused into the LAD and LCX. The regional lactate extraction ratio was measured by GCV and/or CS blood sampling performed either with or without balloon inflation before and during pacing in either LAD or LCX occluded animals. The correlations between the LAD and GCV flow, as well as between the LCX and CS-GCV flow were significant (r=0.96, r=0.93, n=30, p<0.001). The flow distribution by color microspheres in the GCV was 75+/-10% for the LAD, whereas in CS it was 70+/-12% for the LCX. By pacing, the lactate extraction ratio of the drained blood from the ischemic myocardium was +10+/-3% in the GCV blood, whereas it was -10+/-4% (p<0.01) in the CS blood. Thus, this new thermodilution catheter with a balloon was found to be useful for measuring regional coronary hemodynamics and also for evaluating the regional myocardial metabolism.

Disaster and cardiac disease

Evidence obtained over the past decade has revealed that cardiac events and sudden cardiac deaths do not occur randomly but are caused by daily activities and emotional stress. Important triggers may be stress on autonomic nervous tone and sympathetic activities. Such sympathetic activities are changed in a circadian manner with fluctuations in blood rheology and catecholamine secretion. The threshold of electrical instability, left ventricular dysfunction and coronary stenosis may become reduced through the acceleration of sympathetic tone due to emotional stress, thus causing malignant arrhythmia and plaque rupture. Recognition of this multifactorial pathophysiology provides a basis for understanding preventive strategies.

Impaired endothelium-dependent vasodilation in the brachial artery in variant angina pectoris and the effect of intravenous administration of vitamin C

Endothelial dysfunction in the coronary artery contributes to the pathogenesis of variant angina, and endothelial dysfunction in variant angina may be associated with increased oxidant stress in the systemic arteries. We investigated whether endothelial dysfunction exists in the peripheral artery in patients with variant angina, and also examined the effect of vitamin C, an antioxidant, on endothelium-dependent vasodilation. Using high-resolution ultrasound, both the flow-mediated vasodilation (FMD, endothelium-dependent vasodilation) and sublingual nitroglycerin-induced vasodilation (NTG-D, endothelium-independent vasodilation) in the brachial artery were measured in 28 patients with variant angina and 24 control subjects who had normal coronary arteries. FMD was significantly impaired in patients with variant angina compared with control subjects (1.8 +/- 2.2% vs 6.4 +/- 4.9%, p <0.001). FMD and NTG-D before and after intravenous administration of either vitamin C or placebo were measured in 17 patients with variant angina. FMD significantly improved after the administration of vitamin C (from 2.2 +/- 2.4% to 4.5 +/- 1.6%, p <0.01), but not after administration of the placebo (from 2.0 +/- 2.6% to 1.7 +/- 1.9%). The improved FMD due to vitamin C in patients with variant angina, however, was not significantly different from that in the control subjects. NTG-D was not significantly different between patients with variant angina and control subjects (14.0 +/- 7.8% vs 13.6 +/- 5.0%) and it was also not affected by vitamin C.

IN CONCLUSION

(1) FMD in the brachial artery is impaired in patients with variant angina, and (2) the acute administration of the antioxidant, vitamin C, was observed to reverse this endothelial dysfunction. These findings support the theory that the systemic inactivation of nitric oxide due to oxidative stress might exist in patients with variant angina.

Coronary remodeling of proximal and distal stenotic atherosclerotic plaques within the same artery by intravascular ultrasound study

The aim of this intravascular ultrasound study was to compare the type and the degree of vessel remodeling in proximal and distal de novo lesions within the same coronary artery in patients with stable angina pectoris. Seventy-six de novo coronary artery lesions in 38 coronary arteries of 38 patients were imaged by intravascular ultrasound. The vessel area (VA) within the external elastic lamina and the lumen area (LA) were measured, and the wall area (VA-LA) was calculated at the lesion site, and the proximal and distal reference sites. The VA ratio was defined as (lesion VA/average of the proximal and distal reference VAs) to represent the degree of vessel remodeling. The proximal coronary segments showed compensatory enlargement more often (68% vs 29%, p < 0.01) than the distal segments, and the VA ratio at the lesion site was significantly larger (1.1 +/- 0.3 vs 1.0 +/- 0.2, p <0 .01) in proximal segments than in distal segments. The type of coronary remodeling was discordant in 61% and concordant in only 39% of coronary arteries between the proximal and distal segments. The type of coronary remodeling of proximal and distal coronary lesions was inhomogeneous, even within the same vessel. Proximal coronary segments showed more prominent compensatory enlargement than distal segments, which have a similar degree of luminal narrowings.

Clinical validation of intravascular ultrasound imaging for assessment of coronary stenosis severity: comparison with stress myocardial perfusion imaging

OBJECTIVES

To validate intravascular ultrasound (IVUS) measurements for differentiating functionally significant from nonsignificant coronary stenosis.

BACKGROUND

To date, there are no validated criteria for the definition of a flow-limiting coronary artery stenosis by IVUS.

METHODS

Preinterventional IVUS imaging (30-MHz imaging catheter) of 70 de novo coronary lesions was performed. The lesion lumen area and three IVUS-derived stenosis indixes comparing lesion lumen area with the lesion external elastic lamina (EEL) area, the mean reference lumen area and the mean reference EEL area were compared with the results of stress myocardial perfusion imaging.

RESULTS

The lesion lumen area and three IVUS-derived stenosis indexes showed sensitivities and specificities ranging between 80% and 90% using stress myocardial perfusion imaging as the gold standard. The lesion lumen area < or =4 mm2 is a simple and highly accurate criterion for significant coronary narrowing.

CONCLUSIONS

Quantitative IVUS indices can be reliably used for identifying significant epicardial coronary artery stenoses.

Endothelium-dependent flow-mediated vasodilation in coronary and brachial arteries in suspected coronary artery disease

Previous studies showed a weak correlation between endothelial function of the coronary arteries as assessed by acetylcholine and brachial artery vasomotion during reactive hyperemia. When the same stimulus was used, we obtained a strong correlation between flow-mediated dilation in the coronary and brachial arteries (r=0.78, p <0.001), so that noninvasive assessment of flow-mediated dilation in the brachial artery could be used as a surrogate measure for coronary artery endothelial function.

Differences in heart rate variability in the acute phase of first and second attacks of myocardial infarction

The purpose of the study was to examine the differences between first and second myocardial infarctions with respect to improvement in measures of heart rate variability (HRV). The study population comprised 48 non-diabetic patients with acute myocardial infarction (AMI), and with angiographically documented coronary artery occlusion and successful reperfusion. The subjects were grouped as 35 cases with a first AMI attack and 13 with their second AMI. Two weeks after the onset of infarction, indices of HRV were higher in first infarction cases than in second infarction cases. In the latter, there were no significant increases in HRV indices from day of onset to 2 weeks later, nor were there any significant changes in left ventricular ejection fraction (LVEF) from onset to 3 weeks later. All patients studied had a patent infarct-related artery 3 weeks later. We found sustained low values of HRV after a second AMI. Different risk stratification may be needed between uncomplicated first AMI and second AMI cases.

Extent of ischemic stimulus and plasma beta-endorphin levels in silent myocardial ischemia

BACKGROUND

Beta-endorphin has been reported to play a role in the mechanism of silent myocardial ischemia.

OBJECTIVES

Plasma beta-endorphin levels during coronary angioplasty-induced silent and symptomatic myocardial ischemia were compared with those during exercise-induced silent ischemia.

METHODS AND RESULTS

The study population consisted of 40 nondiabetic patients with angioplasty-indicated coronary artery disease. All patients underwent exercise treadmill testing 2 to 4 days before angioplasty. Patients were divided into three groups: group 1, 10 patients with silent ischemia during exercise and angioplasty; group 2, 15 patients with silent ischemia during exercise and symptomatic ischemia during angioplasty; and group 3, 15 patients with symptomatic ischemia during both exercise and angioplasty. In group 1, plasma beta-endorphin levels during balloon inflation were significantly higher than in groups 2 and 3 and also significantly higher than during exercise. In group 2, plasma beta-endorphin levels were significantly elevated at exercise-induced silent myocardial ischemia and balloon-induced symptomatic myocardial ischemia, but the levels between exercise and balloon inflation were not significantly different.

CONCLUSIONS

For "silent" myocardial ischemia, it may be necessary for beta-endorphin levels to increase to sufficiently high levels to suppress anginal symptoms in response to the degree of ischemic stimuli.

Effect of carteolol on silent myocardial ischemia, variability in heart rate, and the pain-modulating system

To investigate the effects of carteolol, which is a nonselective beta-adrenergic agent with intrinsic sympathomimetic activity, on silent myocardial ischemia, exercise-induced myocardial ischemia, indexes of heart rate variability, and pain-modulating system, 20 patients (mean 60 +/- 9 years) with chronic stable angina underwent exercise treadmill testing and 24-hour ambulatory electrocardiographic monitoring during 2 weeks of carteolol administration (15 mg/day) in a double-blind, placebo-controlled design. Plasma levels of beta-endorphin and bradykinin and electrical pain stimulation to the skin were measured at rest and peak exercise. Indexes of heart rate variability of both time-domain and frequency-domain analysis were derived from 24-hour ambulatory electrocardiographic monitoring. Carteolol decreased maximal heart rate responses to daily activities during ambulatory monitoring and significantly reduced the median frequency and duration of silent myocardial ischemic episodes (from 1.0 to 0.0 events/24 hr and from 16 to 0 min/24 hr, respectively). Carteolol significantly decreased the rate-pressure product at rest and during exercise with improving maximal ST segment depression, suggesting amelioration of exercise-induced myocardial ischemia. Carteolol did not significantly affect plasma levels of beta-endorphin and bradykinin or pain threshold. It significantly decreased some indexes (standard deviation of all normal sinus R-R intervals in the entire 24-hour recording and standard deviation of the mean of all 5-minute segments of normal R-R intervals of a 24-hour recording) of heart rate variability. These results suggest that carteolol may reduce total myocardial ischemic burden by the reduction of cardiac oxygen demand during daily activities and exercise stress, while not affecting plasma levels of beta-endorphin, bradykinin, and pain threshold. Because carteolol tended to decrease indexes of heart rate variability, significant caution might be necessary in prescribing the beta-blocking agents with intrinsic sympathomimetic activity like carteolol to patients with potential serious arrhythmia.

Use of head-up tilt testing to determine a possible cause of unexpected cardiac asystole during epidural anesthesia

Head-up tilt testing is widely used in the diagnosis of syncope of unknown origin. In this report, head-up tilt testing elucidated the etiology of cardiac asystole of unexpected and sudden onset during orthopedic surgery under epidural anesthesia in a 30-year-old woman. Conventional diagnostic approaches were ineffective. Venous pooling in the lower legs as a result of vasodilation and subsequent vagotony due to epidural anesthesia, a condition mimicking orthostatic stress, is proposed as the mechanism of asystole. Follow-up examinations over 16 months revealed no further syncope and a good clinical course. Head-up tilt testing was useful in determining etiology in this case.

Heart rate variability and head-up tilt testing in patients with syncope of undetermined etiology

Indices of heart rate variability are non-invasive indicators of neural control of the heart. To investigate the significance of changes in heart rate variability in neurally mediated syncope, we performed head-up tilt testing in 45 patients with syncope of undetermined etiology. Seventeen patients showed a negative response and 28 showed a positive response; 18 had a vasodepressor response (systolic blood pressure dropped > or = 50% without a decrease in heart rate) and 10 had a vasovagal response (systolic blood pressure dropped > or = 50% with a decrease in heart rate of > or = 30%). The mean RR-interval, the standard deviation of normal sinus RR-intervals (standard deviation of RR-interval) and power spectra were measured in consecutive 2 min periods throughout the study. Power spectra consisted of low frequency (0.04-0.15 Hz), high frequency (0.15-0.40 Hz) and total spectra (0.01-1.0 Hz). Both high frequency spectra and the low/high frequency spectra ratio significantly changed with head-up tilt testing regardless of the response. However, high frequency, low frequency and total spectra increased in relation to symptoms. These changes were most profound in the high frequency spectra of subjects with a vasovagal response. Since high frequency spectra reflect parasympathetic tone, a profound change in the high frequency spectra implies that parasympathetic activities play a significant role in patients with a vasovagal response. The assessment of heart rate variability during head-up tilt testing can provide new insight into the pathogenesis of syncope of undetermined etiology.

Methodology of serial ECG classification using an adaptation of the NOVACODE for Q wave myocardial infarction in the Bypass Angioplasty Revascularization Investigation (BARI)

Serial electrocardiographic (ECG) changes are a critical component of the diagnostic algorithm for classification of myocardial ischemic events in large-scale clinical trials. This study describes a computerized serial ECG classification program developed at the St. Louis University Core ECG Laboratory for use in the Bypass Angioplasty Revascularization Investigation (BARI) trial, in which patients with multivessel coronary artery disease were randomized to receive either coronary artery bypass grafting or percutaneous transluminal coronary angioplasty. The St. Louis University program detects and codes serial changes in Q, ST, and T wave items according to Minnesota code (MC) criteria using a modified NOVACODE hierarchical classification system. Measurements using a seven-power calibrated coding loupe are used to generate the MC from a customized software program. Significant minor or major changes are detected by the serial comparison program and referred to a physician coder for verification. Serial comparison coding rules are used to adjust for weaknesses in the standard MC classification system resulting from instability at decision boundaries. Of 4,244 BARI randomized and registry study participants with follow-up ECGs received at the Core ECG Laboratory as of March 1995, a grade 2 MC Q wave progression was noted in 568 participants (13.4%) using MC criteria alone, as compared with 367 (8.6%) after the St. Louis University coding rules were applied. The incidence of grade 1 MC Q wave progressions was 16.4% (697/4,244) versus 6.1% (259/4,244) when the St. Louis University program was applied. Intraobserver variability for grade 2 Q wave progression codes determined from a sample of 812 serial.

Efficacy of direct injection of ethanol into the myocardium to control aconitine-induced ventricular tachycardia in anesthetized dogs

The effect of injecting ethanol directly into the myocardium to control aconitine-induced ventricular tachycardia (VT) was evaluated in anesthetized dogs. In 17 dogs, VT was induced by injecting aconitine (1.0 microgram, median dose) directly into the epicardium. After inducing persistent VT for up to 3 min, 0.6 ml (median volume) of 96% ethanol was injected into the same epicardial region. Regular sinus rhythm reappeared in 15 dogs with no change in systolic blood pressure; the other 2 dogs died of ventricular fibrillation (VF). In another 13 dogs, VT was induced by injecting aconitine directly into the endocardium using a Variocath needle catheter. After persistent VT for up to 3 min, a regular sinus rhythm was restored in 7 dogs by injecting 2.0 ml (median volume) of 96% ethanol; the remaining 6 dogs died of VF. Histology showed no transmural necrosis and the subendocardial necrotic areas were essentially the same in the dogs that recovered from VT as in those that died. There was no statistically significant relationship between doses of ethanol and VT duration. These preliminary results suggest that the injection of ethanol into the myocardium may efficiently terminate VT when other techniques fail.

Arachidonic acid metabolites in acute myocardial infarction

Abnormalities of arachidonic acid metabolism are implicated in spasm and thrombosis in coronary arteries. Therefore, arachidonic acid metabolites were examined in patients with acute myocardial infarction (AMI). Plasma levels of thromboxane B2 (TXB2), 6-keto-prostaglandin F1 alpha (6KPGF1 alpha), leukotriene B4 (LTB4), and slow reacting substance of anaphylaxis (SRS-A) composed of leukotriene C4 (LTC4), leukotriene D4 (LTD4) and leukotriene E4 (LTE4), were measured in 19 AMI patients. Plasma levels of TXB2, LTB4, and SRS-A in systemic artery blood were significantly elevated during the acute stage (within twenty-four hours after the onset of chest pain) of AMI (TXB2, 0.36 ng/mL; LTB4, 0.75 ng/mL; and SRS-A [LTC4+LTD4+LTE4], 0.96 ng/mL compared with those of normal controls (TXB2, 0.18 ng/mL; LTB4, 0.44 ng/mL; and SRS-A (LTC4+LTD4+LTE4], 0.31 ng/mL). These values decreased to near-normal control levels by one month after the AMI attack. The findings in this study suggest that abnormalities of arachidonic acid metabolism accompany, and may play a role in the pathogenesis of, AMI.

Effect of nipradilol on silent myocardial ischemia, plasma beta-endorphin, and bradykinin in chronic stable angina

HYPOTHESIS

This study was undertaken to investigate the effect of nipradilol on the total ischemic burden and on plasma levels of beta-endorphin and bradykinin.

METHODS

Sixteen patients with chronic stable angina were subjected to exercise treadmill testing and 24-h ambulatory electrocardiogram (ECG).

RESULTS

Nipradilol significantly decreased both mean heart rate and mean pressure rate product at submaximal and maximal exercise. It significantly improved exercise-induced maximal ST-segment depression from -2.7 +/- 0.5 mm to -1.3 +/- 0.6 mm (p < 0.05) and reduced the number of leads with significant ST-segment depression (4.0 +/- 1.2 vs. 2.0 +/- 1.8, p < 0.05). Silent ischemic episodes recorded in 24-h ambulatory ECG were significantly decreased by nipradilol administration, concomitantly with a decrement of mean heart rate and observed maximal heart rate. Patients with exercise-induced silent myocardial ischemia showed significantly increased plasma levels of beta-endorphin during both the placebo and nipradilol phases of the study. However, during the nipradilol phase, bradykinin did not change significantly at rest and at peak exercise.

CONCLUSION

Nipradilol effectively controls exercise-induced myocardial ischemia and silent myocardial ischemic episodes, and does not influence the response of plasma levels of beta-endorphin to exercise stress testing in patients with exercise-induced silent myocardial ischemia.

Change of plasma leukotriene C4 during myocardial ischemia in humans

Changes in leukotriene C4 levels during different degrees of myocardial ischemia in humans were examined by comparing radioimmunoassay measures of leukotriene C4 plasma levels obtained during transient and prolonged myocardial ischemia. Leukotriene C4 levels in systemic arterial and coronary sinus blood were determined in patients with chronic stable angina before and after myocardial ischemia induced either by exercise (supine bicycle ergometer exercise stress testing; n = 14; age, 52 +/- 8 years) or by coronary occlusion during angioplasty (n = 14; age 53 +/- 7 years). Temporal changes of leukotriene C4 were also followed in arterial and pulmonary artery blood within 24 h after the onset of chest pain (acute phase), and 1 day, 1 week, and 1 month later in 22 patients with acute myocardial infarction (AMI) (12 patients with thrombolytic therapy, age 61 +/- 10 years; 10 patients without thrombolytic therapy, age 60 +/- 11 years). Clinical characteristics, including coronary risk factors and the severity of coronary artery disease, were not significantly different among the groups. Exercise-induced myocardial ischemia and coronary occlusion did not induce any significant leukotriene C4 changes in the chronic stable angina patients, whereas AMI patients had significantly higher plasma leukotriene C4 levels in both arterial and pulmonary artery blood in the acute phase compared with those of chronic stable angina patients (arterial blood, 471 +/- 164 pg/ml and 477 +/- 235 pg/ml vs. 275 +/- 254 pg/ml or 240 +/- 66 pg/ml, p < 0.05; pulmonary artery blood in AMI, 543 +/- 162 pg/ml vs. 234 +/- 125 pg/ml or 225 +/- 64 pg/ml, coronary sinus blood in chronic stable angina, p < 0.05). These results suggest that leukotriene C4 is involved more in prolonged myocardial ischemia than in transient myocardial ischemia, and that leukocyte function might play a significant role in the pathogenesis of patients with AMI.

Preoperative clinical assessment and dipyridamole thallium-201 scintigraphy for prediction and prevention of cardiac events in patients having major noncardiovascular surgery and known or suspected coronary artery disease

The aim of this study was to assess the relative prognostic use of clinical risk stratification and intravenous dipyridamole thallium-201 scintigraphy in patients with an intermediate to high prevalence of coronary artery disease (CAD) who have undergone major noncardiovascular surgery, and to assess the effects of medical therapy or coronary revascularization based on the result of this clinical scintigraphic screening on perioperative cardiac morbidity and mortality. Patients (n = 161) with an intermediate to high likelihood of CAD had clinical assessment and intravenous dipyridamole planar thallium-201 testing which was analyzed semiquantitatively. Cardiac events were cardiac death (n = 9), nonfatal myocardial infarction (n = 6), acute pulmonary edema (n = 6), and unstable angina (n = 4). Multiple (> or = 2) clinical risk variables predicted any cardiac event (p = 0.04). Presence of multiple (> or = 2) abnormal thallium-201 segments was the only independent predictor of cardiac death or nonfatal myocardial infarction (p < 0.001), and was the most powerful multivariate predictor of any cardiac event (p < 0.002). Patients with an abnormal dipyridamole thallium-201 scan had a higher risk of perioperative cardiac death, myocardial infarction (18% vs 2%; p < 0.001), or any perioperative cardiac event (27% vs 6%; p < 0.001) when compared with those with a normal scan. Preoperative changes in anti-ischemic therapy or coronary revascularization in 36 of 72 patients with abnormal dipyridamole thallium-201 studies reduced perioperative death or myocardial infarction from 31% to 6% (p < 0.01), and all cardiac events from 47% to 8% (p < 0.001) compared with those in patients without intervention.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of bepridil on silent myocardial ischemia and eicosanoid metabolism in chronic stable angina pectoris after healing of myocardial infarction

To investigate the effects of bepridil on silent myocardial ischemia and on eicosanoid metabolism, 10 patients with chronic stable angina underwent exercise treadmill testing and 48-hour ambulatory electrocardiographic monitoring both before and after 4 weeks of bepridil administration (150 mg/day). Fasting venous levels of thromboxane B2, 6-keto-prostaglandin F1 alpha, and leukotriene C4 were measured by radioimmunoassay. Bepridil decreased heart rate responses to daily activities during ambulatory monitoring, and significantly (p < 0.05) reduced the median frequency and duration of silent myocardial ischemic episodes (from 5.5 to 0 events/48 hours and from 86 to 0 minutes/48 hours respectively). Bepridil significantly decreased the blood pressure heart rate product at peak exercise and significantly prolonged the mean exercise tolerance time (from 456.6 to 527.0 second). Bepridil also significantly decreased the plasma levels of thromboxane B2 and leukotriene C4 at rest. These results suggest that bepridil may reduce silent myocardial ischemic episodes either by the reduction of cardiac oxygen demand during daily activities and exercise stress, or by controlling coronary and systemic vasomotor tone. The drug also has a salutary effect on eicosanoid metabolism, to which its efficacy on silent myocardial ischemic episodes may be related.