Coronary flow, VO2 peak and anaerobic threshold in patients with dilated cardiomyopathy

BACKGROUND

Coronary flow is influenced by several determinants and may change according to external stimuli. In patients with dilated cardiomyopathy (DC), adaptive mechanisms could induce alterations in coronary flow, possibly related to oxygen consumption.

METHODS

In 67 consecutive patients with DC (mean age 52.06+/-13.84, 52 male gender, left ventricle ejection fraction (LVEF) 29.49%+/-8.68) and normal coronary angiography findings, coronary flow in left anterior descending (LAD), right coronary artery (RC) and left circumflex (LCx) was reported as TIMI frame count (TFC). All patients underwent a cardiopulmonary test with VO2 peak and anaerobic threshold (AT) measurement, New York Heart Association (NYHA) class stratification, two-dimensional echocardiographic evaluation including LVEF and left ventricle end-diastolic diameter (LVEDD) assessment. All patients were receiving optimal medical treatment.

RESULTS

In a multivariate analysis, a statistically significant correlation was found between VO2 peak and TFC (B 7.61, p<0.001, R2 0.61 for LAD; B 3.42, p<0.001, R2 0.33 for RC); an inverse correlation was found between AT and TFC (B -9.77, p<0.001, R2 0.61 for LAD; B -4.26, p<0.001, R2 0.33 for RC).

CONCLUSIONS

Coronary flow is related to VO2 peak and AT in patients with DC, suggesting a "compensatory" mechanism.

Free testosterone plasma levels are negatively associated with the intima-media thickness of the common carotid artery in overweight and obese glucose-tolerant young adult men

OBJECTIVE

To evaluate the relation between free testosterone (FT) levels and the intima-media thickness of the common carotid artery (IMT-CCA) in overweight and obese glucose-tolerant (NGT) young adult men.

DESIGN

Cross-sectional study of FT and IMT-CCA in obese men.

SUBJECTS

A total of 127 overweight and obese NGT male individuals, aged 18-45 y.

MEASUREMENTS

FT plasma levels; IMT-CCA, as measured by high-resolution B-mode ultrasound imaging; central fat accumulation, as evaluated by waist circumference; body composition, as measured by bioimpedance analysis; insulin resistance, as calculated by homeostatic model assessment (HOMA(IR)); systolic and diastolic blood pressure; and fasting concentrations of glucose, insulin, and lipids.

RESULTS

IMT-CCA was positively correlated with age, body mass index (BMI), fat mass (FM), waist circumference, and fasting glucose concentrations, and inversely associated with FT levels. After multivariate analysis, IMT-CCA maintained an independent association with BMI, FM, and FT levels. This study indicates that IMT-CCA is negatively associated with FT levels, independent of age, total body fat, central fat accumulation, and fasting glucose concentrations in overweight and obese NGT patients.

CONCLUSION

Hypotestosteronemia may accelerate the development of atherosclerosis and increase the risk for CHD in obese men.

Management of patients with syncope referred urgently to general hospitals

OBJECTIVE

To evaluate the incidence and the strategy of management of syncope admitted urgently to a general hospital.

BACKGROUND

The management of patients with syncope is not standardized.

METHODS

The study was a prospective observational registry from a sample of 28 general hospitals in Italy and enroled all consecutive patients referred to their emergency rooms from November 5th 2001 to December 7th 2001 who were affected by transient loss of consciousness as the principal symptom.

RESULTS

The incidence of syncope was 0.95% (996 of 105,173 patients attending). Forty-six percent were hospitalized, mostly in the Department of Internal Medicine. The mean in-hospital stay was 8.1+/-5.9 days. A mean of 3.48 tests was performed per patient. A definite diagnosis was made in 80% of cases, neurally-mediated syncope being the most frequent. The findings of each of the 28 hospitals participating in the survey were separately evaluated. We observed great inter-hospital and inter-department heterogeneity regarding the incidence of emergency admission, in-hospital pathways, most of the examinations performed and the final assigned diagnosis. For example, the execution of carotid sinus massage ranged from 0% in one hospital to 58% in another (median 12.5%); tilt testing ranged from 0 to 50% (median 5.8%); the final diagnosis of neurally-mediated syncope ranged from 10 to 78.6% (median 43.3%).

CONCLUSION

Great inter-hospital and inter-department heterogeneity in the incidence and management of syncope was observed in general hospitals. As a consequence, we were unable to describe a uniform strategy for the management of syncope in everyday practice.

Whole-body bioelectrical impedance analysis in patients with chronic heart failure: reproducibility of the method and effects of body side

BACKGROUND

Fluid imbalance and malnutrition have an important role in the clinical setting of chronic heart failure (CHF). Recently, tetrapolar bioelectrical impedance analysis has been suggested as an attractive method which may be used in the clinical assessment of the body composition. The aim of this study was to determine the effects of body side on whole bioelectrical impedance analysis parameters and test-retest reliability, prior to its use in a large cohort of patients.

METHODS

In 114 consecutive patients with CHF (mean age 65 +/- 10 years, left ventricular ejection fraction 31 +/- 9%, NYHA functional class 2.6 +/- 0.9) we measured the total body resistance, the reactance and the derived angle phase using a single-frequency (50 KHz) tetrapolar plethysmograph device. The evaluations were performed on the left and right sides of the body, in a random order, on two different occasions 30 min apart. The effects of body side were analyzed by the Student's t-test and the test-retest reliability was computed by using the coefficient of variation and intraclass correlation coefficient.

RESULTS

In both evaluations, the mean resistance value of the right side was significantly lower (almost 10 ohms) than that of the left side, the reactance was not different, and as a consequence the angle phase was significantly higher (almost 0.1 degrees) in the right than in the left side. The test-retest reliability for all the measurements considered was very high (the intraclass correlation coefficient ranged from 0.95 to 0.99 and the coefficient of variation from 1.7 to 4.3%).

CONCLUSIONS

In CHF, the body side is important for the whole-body assessment of the resistance and the angle phase, but not for reactance. In addition, all these measurements are characterized by an excellent test-retest reliability and, consequently, do not necessitate a substantial increase in the sample size for the detection of small differences in experimental studies.

Plasma leptin is independently associated with the intima-media thickness of the common carotid artery

OBJECTIVE

To investigate whether intima-media thickness (IMT) of the common carotid artery (CCA), an early marker of asymptomatic atherosclerosis, is significantly and independently associated with plasma concentrations of leptin, an adipose tissue hormone that has recently been proposed as a cardiovascular risk factor in obese patients.

DESIGN

Cross-sectional sample of normal-weight and obese men and women.

SUBJECTS

One-hundred and twenty healthy subjects (52 men and 68 women), aged 18-45 y and with a wide range of BMI, were recruited for the study.

MEASUREMENTS

Fasting plasma leptin concentrations and the IMT of the CCA were measured in all subjects. Leptin concentrations were measured by radioimmunoassay and the IMT of the CCA was quantified by high resolution B-mode ultrasound imaging. Central fat (measured by waist circumference), smoking habits, blood pressure, insulin sensitivity (measured by the insulin tolerance test), and fasting plasma glucose, insulin and lipid pattern (cholesterol, HDL-cholesterol, triglycerides, LDL-cholesterol) were also measured.

RESULTS

IMT of the CCA was positively correlated with log leptin concentrations (P<0.005 in men and P<0.001 in women), body mass index (P<0.001 in men and women), waist circumference (P<0.001 in men and women), age (P<0.001 in men and P<0.05 in women), and negatively associated with insulin sensitivity in both sexes (P<0.05). IMT was also directly correlated with cholesterol (P<0.05), LDL-cholesterol (P<0.01) and systolic blood pressure in men (P<0.05), and with diastolic blood pressure levels in women (P<0.05). When a multiple linear regression model was used without body mass index (BMI), the correlation between leptin and IMT was maintained in both men (P<0.01) and women (P<0.005), independent of age, insulin sensitivity, smoking habits, systolic blood pressure, fasting glucose, triglycerides, cholesterol, LDL-cholesterol and HDL-cholesterol. By contrast, BMI-adjusted leptin concentrations were not significantly associated with IMT (Pc (partial correlation): 0.41 in men and 0.15 in women). Moreover, when BMI was entered into a multiple linear regression model without leptin, the correlation between BMI and IMT was maintained in both men (P<0.005) and women (P<0.01), independent of the same parameters.

CONCLUSION

Plasma leptin concentrations are independently associated with the IMT of the CCA, suggesting that the increase of adipose tissue mass (or leptin per se) may have an unfavourable influence on the development of atherosclerosis. However, the association between IMT and leptin seems to be dependent and/or confounded by the relationship between IMT and obesity.

[Cardiopulmonary sensitivity and chemosensitivity]

The autonomic control of the cardiovascular system plays an important role in maintaining the arterial pressure at the levels necessary for adequate tissue perfusion. In cardiovascular diseases, the impairment of the basic reflex mechanisms that are responsible for the moment-to-moment regulation could increase sympathetic activity and is correlated with an adverse outcome. The objective of the present review was to provide information about the methodological aspects exploring cardiopulmonary and chemoreceptor reflexes. Different techniques are available and all of them include assessment of reflexes through the activation or deactivation of either the cardiopulmonary baroreceptors or chemoreceptors. Intravenous saline load, head-down tilt, passive legs raising, head-out water immersion and the application of a lower body positive pressure are the principal methods utilized for activating cardiopulmonary baroreceptors; on the contrary deactivation could be achieved by acutely induced hypovolemia by furosemide or blood donation, inflation of a congestion cuff on the thighs or application of a negative pressure on the lower body. The transient exposure to a hypoxic or a hypercapnic gas mixture is frequently used to determine the peripheral and central chemoreflexes, respectively. The reflexes are quantified by the gain between output (i.e. heart rate, sympathetic activity, vascular resistance, ventilation) and input (oxygen saturation, end-tidal CO2 or changes in central venous pressure). One important limitation in assessing the cardiopulmonary baroreflex by using currently available techniques is that the involvement of the arterial baroreflex cannot be avoided. In addition, chemoreflexes cannot be interpreted unless the breathing rate is controlled. To date, several techniques are available for the quantification of cardiopulmonary baroreceptor and chemoreceptor reflexes and could provide new information on the abnormal autonomic mechanisms contributing to the pathophysiology of several cardiovascular diseases.

Depression but not anxiety influences the autonomic control of heart rate after myocardial infarction

AIMS

It has been previously hypothesized that the adverse outcome observed in depressed patients after myocardial infarction might be due to an imbalance in autonomic nervous system activity. The aim of this study was to define the role of depressive and anxious symptoms in influencing autonomic control of heart rate after myocardial infarction.

METHODS AND RESULTS

The SD of RR intervals, baroreflex sensitivity, and depression and anxiety (Zung's scales) were assessed before discharge in 103 patients with acute myocardial infarction; 32 were found to be depressed. Among the patients who were not taking beta-blockers, those with depression had significantly lower SDs of RR intervals and baroreflex sensitivity than did those without depression (96.3 +/- 22.2 ms vs 119.5 +/- 37.7 ms, P =.016; 8.6 +/- 6.2 ms vs 11.8 +/- 6.5 ms/mm Hg, P =.01, respectively). No differences were found when anxiety was considered or when beta-blockers were given. Among the patients not taking beta-blockers, there was a significant correlation between depression levels and both the SD of RR intervals (r = -0.47) and baroreflex sensitivity (r = -0.40).

CONCLUSIONS

In patients with myocardial infarction, depression but not anxiety negatively influences autonomic control of heart rate. Beta-blockers modify these influences.

Ticlopidine versus aspirin after myocardial infarction (STAMI) trial

OBJECTIVES

We sought to compare the efficacy of aspirin and ticlopidine in survivors of acute myocardial infarction (AMI) treated with thrombolysis.

BACKGROUND

The role of ticlopidine in secondary prevention after AMI has not yet been explored.

METHODS

Of 4,696 patients with AMI treated with thrombolysis who were screened, 261 died in the hospital (5.6%) and 1,470 were enrolled in this randomized, double-blind, multicenter trial and allocated to treatment with either aspirin (160 mg/day) or ticlopidine (500 mg/day). The most frequent reasons for exclusion were refusal to give informed consent, planned myocardial revascularization, risk of noncompliance with study procedures, need for anticoagulant therapy and contraindications to the study treatments. The primary end point was the first occurrence of any of the following events during the six-month follow-up: fatal and nonfatal AMI, fatal and nonfatal stroke, angina with objective evidence of myocardial ischemia, vascular death or death due to any other cause.

RESULTS

The primary end point was recorded in 59 (8.0%) of the 736 aspirin-treated and 59 (8.0%) of the 734 ticlopidine-treated patients (p = 0.966). Vascular death was the first event in five patients taking aspirin and in six patients taking ticlopidine (0.7% vs. 0.8%; p = NS); nonfatal AMI in 18 and 8 (2.4% vs. 1.1%; p = 0.049); nonfatal stroke in 3 and 4 (0.4% vs. 0.5%; p = NS); and angina in 33 and 40 (4.5% vs. 5.4%; p = NS), respectively. The frequency of adverse reactions was not significantly different between the two groups.

CONCLUSIONS

No difference was found between the ticlopidine and aspirin groups in the rate of the primary combined end point of death, recurrent AMI, stroke and angina.

Usefulness of handgrip to improve ibutilide efficacy in organizing atrial electrical activity during atrial fibrillation

We analyzed the effect of handgrip on atrial electrical activity during atrial fibrillation (AF) by recording right and left atrial activity in 15 patients with persistent AF under baseline conditions and after saline and ibutilide infusions. The handgrip test for 15 seconds, which was always associated with a significant increase in mean atrial cycle length, was recorded in both atria (right atrium: saline vs saline + handgrip 141 +/- 29 vs 171 +/- 24 ms, p <0.001; ibutilide vs ibutilide + handgrip: 197 +/- 43 vs 221 +/- 39 ms, p <0.005). Handgrip favorably modifies atrial electrophysiologic properties during AF.

Effect of intermittent subdiastolic pressure in thigh cuffs on human arterial baroreflex

BACKGROUND

We investigated the effects of subdiastolic variations of the pressure inside the thigh cuffs on cardiovascular oscillations and arterial baroreflex sensitivity in humans.

METHODS

During 10 min of controlled breathing at low (0.1 Hz) and high (0.25 Hz) frequencies, 30 healthy subjects underwent variations of the pressure inside the thigh cuffs (from 0 to 40 mmHg) at 0.25 and 0.1 Hz respectively; the periods of controlled breathing without cuff pressure modulation were used as a control. The frequency responses of cardiovascular signals were assessed using spectral analysis, and baroreflex sensitivity by the sequence method.

RESULTS

Cuff pressure modulation at 0.25 Hz did not affect the RR interval, arterial pressure, or baroreflex sensitivity; at 0.1 Hz it did not change the RR interval and arterial pressure, but engaged (0.76 +/- 0.2 of coherence) and increased the low frequency oscillations of the RR interval (from 5.6 +/- 1 to 6.1 +/- 0.9 ln ms2, p < 0.05) and improved baroreflex sensitivity by 25% (from 14.2 +/- 9 to 17.7 +/- 10 ms/mmHg, p < 0.01).

CONCLUSIONS

Subdiastolic thigh cuff pressure modulation at 0.1 Hz improved the low frequency oscillations of heart rate and baroreflex sensitivity. This approach represents a new and simple non-pharmacological strategy for acutely improving baroreflex sensitivity in humans.

Influence of gender and family history of hypertension on autonomic control of heart rate, diastolic function and brain natriuretic peptide

OBJECTIVE

To verify in a unitary view whether autonomic control of heart rate and cardiac structure and function are modified early in offspring of hypertensive families.

METHODS AND RESULTS

We selected 87 age- and sex-matched young normotensive subjects with (n = 45) and without (n = 42) a family history of hypertension who underwent evaluations of arterial pressure, time-domain parameters of autonomic heart rate control (24-h ECG monitoring), spectral baroreflex sensitivity, left ventricular geometry and function (echo-Doppler) and plasma brain natriuretic peptide levels (BNP). The group with a family history of hypertension significantly differed from their counterparts for systolic pressure (119 +/- 11 versus 114 +/- 9 mmHg, P< 0.05), heart rate (RR interval, 766 +/- 64 versus 810 +/- 93 ms, P< 0.05), heart rate variability [the standard deviation of normal RR intervals (SDNN), 147 +/- 29 versus 171 +/- 33 ms, P < 0.051, diastolic function (isovolumetric relaxation time, 65 +/- 9 versus 60 +/- 8 ms, P< 0.05) and BNP (23 +/- 13 versus 37 +/- 10 pg/ml, P< 0.05). Baroreflex sensitivity values did not differ between the two groups. When gender was considered, all the above-mentioned measures, as well as baroreflex sensitivity, were significantly different between males with and without a family history of hypertension but not between females, except for BNP, which was lower in males and females with a history of hypertension (males, 24 +/- 11 versus 38 +/- 8 pg/ml, P< 0.01; females 21 +/- 14 versus 36 +/- 13 pg/ml, P < 0.05).

CONCLUSIONS

Male, but not female, hypertensive offspring have modified diastolic function and autonomic control of heart rate; BNP is the only parameter able to characterize hypertensive offspring independently from the influence of gender. This provides the hypothesis that the impaired production of this hormone could play a primary role in the pre-hypertensive state.

Lower insulin sensitivity as an independent risk factor for carotid wall thickening in normotensive, non-diabetic, non-smoking normal weight and obese premenopausal women

OBJECTIVE

Increased thickness of the intima-media complex of the common carotid artery (IMT-CCA) is an early marker of atherosclerosis. The aim of the present study was to investigate the relationship between insulin resistance and IMT-CCA in premenopausal women.

SUBJECTS

86 young women, aged 18-31 y, were recruited for the study: 28 were normal weight (BMI<25 kg/m2), 23 were overweight (BMI 25-30 kg/m2) and 35 were obese (BMI>30 kg/m2).

MEASUREMENTS

The IMT-CCA was measured by high resolution 'B-mode' ultrasonography; insulin sensitivity was determined by insulin tolerance test (ITT) and quantitated by calculation of KITT. Fasting plasma glucose and lipids (triglycerides, total and HDL-cholesterol) were also measured by enzymatic methods. Central fat accumulation was evaluated by measuring waist circumference (WC).

RESULTS

IMT-CCA showed an inverse association with KITT (P<0.05). When the IMT-CCA was considered as the dependent variable in a forward stepwise multiple regression analysis, it maintained an independent association with KITT (P<0.05), after adjusting data for age, BMI, WC, mean blood pressure levels and plasma glucose and lipids.

CONCLUSION

These results suggest that IMT-CCA is significantly associated with insulin resistance, independent of other well-known CVD risk factors. Since the IMT-CCA is an earlier asymptomatic sign of atherosclerosis, this study indicates that insulin resistance per se may accelerate atherogenesis.

Low-dose dobutamine responsiveness in idiopathic dilated cardiomyopathy: relation to exercise capacity and clinical outcome

AIMS

To evaluate myocardial contractile reserve using low-dose dobutamine echocardiography in patients with chronic heart failure secondary to idiopathic dilated cardiomyopathy stratified by peak exercise oxygen consumption (VO(2)).

METHODS AND RESULTS

Sixty clinically stable patients (56+/-11 years; 45 males) with idiopathic cardiomyopathy and NYHA class I to III symptoms of heart failure were studied and followed-up for 13+/-3 months. All patients underwent cardiopulmonary exercise testing and low-dose dobutamine. The dobutamine infusion protocol consisted of an initial dose of 2.5 micro. kg(-1)per 3 min, increasing by 2.5 micro. kg(-1)per min every 3 min; the maximal dose was 10 micro. kg(-1)per min. The end-systolic volume index, left ventricular ejection fraction and cardiac output were measured at baseline and peak dobutamine dose and their change calculated as ((peak dose value-baseline value)/baseline value]x100. Ten normal subjects with normal left ventricular function and no coronary artery lesions served as a control group to compare low-dose dobutamine results. All analysed echocardiographic variables either at baseline or following dobutamine infusion were significantly lower in patients with chronic heart failure as a whole compared to the control group. When the patients were grouped according to Weber's classification, a statistically significant decrease in percentange changes in end-systolic volume index (rho=-0.77;P<0.0001), left ventricular ejection fraction (rho=-0.72;P<0.0001) and cardiac output (rho=-0. 82;P<0.0001) from class A to class C was observed. The mean percentage decrease in end-systolic volume index following the dobutamine infusion was 28.7+/-9% in class A (peak VO(2)>20 ml. kg(-1). min(-1)), 18.6+/-8% in class B (peak VO(2)between 16 and 20 ml. kg. min(-1)), and only 6.4+/-6% in class C (peak VO(2)between 10 and 16 ml. kg(-1). min(-1)) patient groups. At multivariate analysis, only the percentage change in end-systolic volume index was significantly associated with a peak VO(2)<15 ml. kg(-1). min(-1)(P=0.006). During the follow-up, 17 patients had events (15 readmissions for worsening heart failure and two deaths). At multivariate analysis, only the percentage change in end-systolic volume index was significantly associated with the occurrence of events (P=0.003). The area under the receiver operating characteristic curve for percentage change in end-systolic volume index was not significantly different from that for peak VO(2)(0. 86+/-0.04 vs 0.80+/-0.06;P:ns).

CONCLUSION

This study indicates that in patients with chronic heart failure secondary to idiopathic cardiomyopathy, the cardiac response to low-dose dobutamine, as assessed by echocardiography, is correlated with peak VO(2), an objective and accurate measure of the severity of the disease and clinical outcome.

Influence of hydrophilic and lipophilic beta-blockers on heart rate, ventricular repolarization and their interrelationship in normal subjects

BACKGROUND

It has been hypothesized that hydrophilic and lipophilic beta-blockers have different antiarrhythmic properties because only the latter seem to reduce the rate of sudden death in post-myocardial infarction patients as well as animal models which seem to be independent of their effect on autonomic nervous system modulation. The aim of this study was to evaluate the different effects of a hydrophilic (nadolol) and lipophilic (metoprolol) beta-blocker on ventricular repolarization in normal subjects.

METHODS

Seventeen normal subjects entered this randomized, single-blind cross-over study designed to compare the effects of nadolol (80 mg/day) and slow-release metoprolol (200 mg/day) on dynamic ventricular repolarization. The RR intervals, the QT evaluated at the apex (QT apex) and at the end (QT end) of the T wave before and after correction for heart rate, the standard deviation of QT apex and QT end, and the slope of the QT/RR linear relationship (QTa-slope and QTe-slope) were studied using the ELATEC system (ELA Medical, Mountrouge, France), and an evaluation was made of their reproducibility and the effects of each beta-blocker.

RESULTS

The most reproducible parameters were QT apex, corrected QT apex and the QTe-slope. Nadolol was associated with a greater adrenergic blockade than metoprolol (lengthening of RR interval +25 +/- 7 and +17 +/- 8% respectively, p = 0.0003) and a lower effect on ventricular repolarization (reduction of corrected QT apex -0.6 +/- 3 and -2.5 +/- 2.1% respectively, p < 0.01; reduction of QTe-slope -5 +/- 16 and -15 +/- 15% respectively, p = 0.03).

CONCLUSIONS

At the dosages used in the study, metoprolol showed lower adrenergic blockade but greater effect on ventricular repolarization than nadolol.

Early administration of verapamil after thrombolysis in acute anterior myocardial infarction. Effect on left ventricular remodeling and clinical outcome. VAMI Study Group. Verapamil Acute Myocardial Infarction

BACKGROUND

The administration of verapamil during the reperfusion phase of acute myocardial infarction can reduce the extent and severity of microvessel damage and limit myocardial dysfunction. We aimed at investigating the effect of early verapamil administration on left ventricular remodeling and the clinical evolution after myocardial infarction.

METHODS

Eighty-eight patients with first acute anterior myocardial infarction thrombolysed < 4 hours from symptom onset were enrolled in a multicenter, randomized, double-blind, controlled study of verapamil administration (5 mg i.v. + 2 microg/kg/min over 24 hours). Echocardiographic end-diastolic (EDV) and end-systolic (ESV) left ventricular volumes were assessed by biplane Simpson's rule.

RESULTS

At 90 days, EDV in the verapamil and placebo groups was respectively 88.9 +/- 27.8 and 95.8 +/- 30.7 ml (p = 0.11), ESV was 52.6 +/- 22.7 and 57.7 +/- 25.4 ml (p = 0.18). There was no change over time in the verapamil group (day 3 vs day 90: EDV 85.0 +/- 17.7 vs 88.9 +/- 27.8 ml, p = NS; ESV 48.7 +/- 14.1 vs 52.6 +/- 22.7 ml, p = NS) while left ventricular volume increased in the placebo group (day 3 vs day 90: EDV 87.6 +/- 21.1 vs 95.8 +/- 30.7 ml, p = 0.03; ESV 52.0 +/- 16.9 vs 57.7 +/- 25.4 ml, p = 0.08). NYHA functional classes were differently distributed at 30 and 90 days (chi2 = 0.009 and 0.07), with a lower prevalence of classes II and III in the verapamil group (p = 0.03).

CONCLUSIONS

The early intravenous administration of verapamil in thrombolysed patients can reduce left ventricular remodeling and NYHA functional class after acute anterior myocardial infarction.

Age effect on phase relations between respiratory oscillations of the RR interval and systolic pressure

Spectral analysis may allow the evaluation of (baroreflex) gain and phase between the RR interval and systolic pressure oscillations synchronous with respiration but, unlike baroreflex gain, the determinants of phase are not completely understood. We evaluated the correlates of spectral phase in 92 healthy subjects (44 men) aged 10-80 years. To do so, the cardiorespiratory signals during paced breathing at 16 breaths/min were continuously recorded and analyzed. In addition, respiratory sinus arrhythmia and baroreflex gain (two indices of cardiac vagal activity) and phase were calculated by using an autoregressive spectral technique. At univariate analysis, the phase correlated with age (r = 0.48, P < 0.001), the RR interval (r = 0.32, P < 0.01), respiratory sinus arrhythmia (r = -0.3, P < 0.01), baroreflex gain (r = -0.29, P < 0.01), and body mass index (r = 0.25, P < 0.05). At multivariate analysis, age was the most important physiological correlate of phase, accounting for 23% of interindividual phase variation. Cardiac vagal activity measures (which were higher in women than men) and the RR interval were also significant independent correlates of phase. We conclude that in addition to the RR interval and cardiac vagal activity, age has a significant impact on the phase relationship between respiratory related oscillations of the RR interval and systolic blood pressure. This spectral measure may contain additional information concerning the mechanisms that influence cardiovascular rhythms.

Microcirculatory damage of common carotid artery wall in obese and non obese subjects

The objective of the present study was to determine whether the intima-media thickness (IMT) is independently related with obesity, and central fat accumulation in healthy subjects. Common carotid artery IMT, parameters of body fat accumulation and distribution (body mass index, waist circumference, waist-to-hip ratio), blood pressure levels, and circulating fasting insulin, glucose, and lipid (cholesterol, HDL-cholesterol, triglycerides, LDL-cholesterol) levels were determined in a population of non-diabetic normal weight and obese subjects. Smoking habits (packs-years) were also taken into account. 239 healthy subjects (143 women and 96 men), with age ranging between 18 and 45 years, were enrolled into the study. They were divided indo two groups according to the body mass index (BMI), obese (132 subjects, 77 woman and 55 men, with BMI greater than 27.0) and controls (107 subjects: 66 women and 41 men, with BMI lower than 27.0). Common carotid artery intima-media thickness was measured by B-mode ultrasound imaging. Fasting plasma metabolic parameters (glucose and lipids) and insulin levels were determined by enzymatic and radioimmunological assays, respectively. Insulin sensitivity was estimated by insulin tolerance test (ITT) and the rate constant for plasma glucose disappearance (KITT) during the 3- to 15-min period following the regular insulin injection was taken as a measure of in vivo insulin action. Obese patients showed higher IMT than controls, and IMT was significantly associated with BMI in the whole population (r = 0.316, p < 0.001). Age (r = 0.327, p < 0.001), KITT (r = -0.201, p < 0.01), fasting blood glucose (r = 0.187, p < 0.01), LDL-chol (r = 0.201, p < 0.01), smoking (r = 0.147, p < 0.05), MBP levels (r = 0.154, p < 0.05), cholesterol (r = 0.152, p < 0.05) and HDL-chol (r = -0.159, p < 0.05) were also significantly associated with IMT. Age (r = 0.330, p < 0.05), BMI (r = 0.299, p < 0.01), waist (r = 0.312, p < 0.001), WHR (r = 0.266, p < 0.001) and KITT (r = -0.259, p < 0.01) were the parameters most strongly correlated with IMT in women, and age (r = 0.324, p < 0.001), BMI (r = 0.338, p < 0.001) waist (r = 0.325, p < 0.001) and LDL-chol (r = 0.283, p < 0.01) where the parameters most strongly correlated with IMT in men. When a stepwise multiple regression analysis was performed for the whole population, only age (p < 0.001) and BMI (p < 0.001) maintained a significant positive relationship with IMT. When a stepwise multiple regression analysis was performed separately for men and women, BMI or waist circumference or WHR were alternatively entered into the model; interestingly, only age, BMI and waist were still significantly correlated with IMT, whereas WHR did not maintain a significant correlation with IMT. In conclusion, BMI and waist circumference, but not WHR, are strongly and independently associated with the IMT of common carotid artery. These results suggests that central fat accumulation may accelerate the development of earlier clinically silent stages of atherosclerosis, thus possibly explaining the higher prevalence of cardiovascular diseases in patients with abdominal obesity.

Respiratory systolic pressure variability during atrial fibrillation and sinus rhythm

Previous studies have found that respiratory variations of ventricular response in atrial fibrillation are infrequent and inconsistent. This asynchrony between heart rate and respiration may characterize the physiological mechanisms coupling heart rate and systolic blood pressure oscillations in the respiratory band. The aim of this study was to evaluate whether synchronous variations in systolic blood pressure and respiration depend on a simultaneous change in heart rate. Univariate and bivariate spectral analyses were made of the R-R interval, systolic blood pressure, and respiratory signals during controlled respiration (16 breaths/min) in 24 patients with atrial fibrillation before and after efficacious electrical cardioversion and in 24 age- and sex-matched control subjects. During atrial fibrillation, the spectral coherence between respiration and heart rate was low (0.18+/-0.03), but there was a high level of coherence between respiration and systolic blood pressure (0.67+/-0.05). After cardioversion, the coherence between respiration and heart rate increased to 0.86+/-0.04, whereas the geometric mean values of the concomitant respiratory systolic blood pressure oscillations decreased by 72% (from 21.1 to 5.9 mm Hg(2), P<0.001), which was similar to that observed in the control group (5. 7 mm Hg(2)). These results confirm the inconsistent effect of respiration on heart rate response during atrial fibrillation and demonstrate that respiratory sinus arrhythmia is not a prerequisite for systolic blood pressure oscillations but may play an antioscillatory role in respiratory systolic blood pressure variability, which is probably mediated by arterial baroreflex mechanisms.

A prospective, randomized, comparison in patients between a pectoral unipolar defibrillation system and that using an additional inferior vena cava electrode

The decrease of defibrillation energy requirement would render the currently available transvenous defibrillator more effective and favor the device miniaturization process and the increase of longevity. The unipolar defibrillation systems using a single RV electrode and the pectoral pulse generator titanium shell (CAN) proved to be very efficient. The addition of a third defibrillating electrode in the coronary sinus did not prove to offer advantages and in the superior vena cava showed only a slight reduction of the defibrillation threshold (DFT). The purpose of this study was to determine whether the defibrillation efficacy of the single lead unipolar transvenous system could be improved by adding an electrode in the inferior vena cava (IVC). In 17 patients, we prospectively and randomly compared the DFT obtained with a single lead unipolar system with the DFT obtained using an additional of an IVC lead. The RV electrode, Medtronic 6936, was used as anode (first phase of biphasic) in both configurations. A 108 cm2 surface CAN, Medtronic 7219/7220 C, was inserted in a left submuscular infraclavicular pocket and used as cathode, alone or in combination with IVC, Medtronic 6933. The superior edge of the IVC coil was positioned 2-3 cm below the right atrium-IVC junction. Thus, using biphasic 65% tilt pulses generated by a 120 microF external defibrillator, Medtronic D.I.S.D. 5358 CL, the RV-CAN DFT was compared with that obtained with the RV-CAN plus IVC configuration. Mean energy DFTs were 7.8 +/- 3.6 and 4.8 +/- 1.7 J (P < 0.0001) and mean impedance 65.8 +/- 13 O and 43.1 +/- 5.5 O (P < 0.0001) with the RV-CAN and the IVC configuration, respectively. The addition of IVC significantly reduces the DFT of a single lead active CAN pectoral pulse generator. The clinical use of this biphasic and dual pathway configuration may be considered in patients not meeting implant criteria with the single lead or the dual lead RV-superior vena cava systems. This configuration may also prove helpful in the use of very small, low output ICDs, where the clinical impact of ICD generator size, longevity, and related cost may offset the problems of dual lead systems.

Automatic activity of a decremental long atrioventricular accessory pathway: an unusual feature

The electrophysiological properties of decremental atrioventricular and atriofascicular pathways are not completely understood. We report the case of a patient with fast reentrant tachycardia due to a decremental long atrioventricular pathway, who showed a slow automatic tachycardia arising from the same pathway that was successfully eliminated by radiofrequency catheter ablation.

Diastolic dysfunction and baroreflex sensitivity in hypertension

The determinants of diastolic dysfunction in patients with systemic hypertension are not completely known. To evaluate the possible role of age, arterial blood pressure, and baroreflex heart rate response impairment in causing diastolic dysfunction, we studied 61 patients (42 male; mean+/-SD age, 43.9+/-12 years) with newly recognized and therefore previously untreated systemic hypertension. Diastolic dysfunction was evaluated by means of Doppler echocardiography (and diagnosed as such when the early to atrial peak velocity ratio corrected to heart rate was <1), arterial blood pressure by 24-hour ambulatory monitoring, and baroreflex heart rate response by means of the spectral technique (alpha index) during paced (0.27 Hz) and spontaneous breathing (in a supine position and during tilt). Nineteen patients had diastolic dysfunction, the most powerful predictor of which was age (r=-0.63, P<0.001). The patients with diastolic dysfunction had significantly lower values for spectral baroreflex gain in the high-frequency band than those without (5.2+/-3 versus 8.4+/-5 ms/mm Hg during paced breathing, P<0.05; 7. 4+/-4 versus 13.3+/-7 ms/mm Hg in a supine position, P<0.05; 4.3+/-4 versus 5+/-2 ms/mm Hg during tilt, P<NS). Ambulatory blood pressure values were not significantly different in the patients with (137+/-14 and 89+/-9 mm Hg) and without (144+/-11 and 82+/-24 mm Hg) diastolic dysfunction. In conclusion, age and impaired baroreflex heart rate response (but not pressure overload) are determinants of left ventricular diastolic dysfunction in patients with newly recognized and untreated systemic hypertension.

[Radiofrequency transcatheter ablation of a bidirectional decremental accessory atrioventricular pathway in the coronary sinus]

We report the case of a 63-year-old patient who underwent radiofrequency catheter ablation of an atrioventricular accessory pathway with bidirectional decremental conduction properties. The successful ablation site was the distal end of a wedge-shaped dilation of the first tract of the coronary sinus. Atrioventricular accessory pathways with anterograde decremental conduction properties was thought to belong to fibers with Mahaim type electrophysiological properties. They rarely show decremental retrograde conduction properties. Most Mahaim type atrioventricular pathways are right-sided with atrial insertion points at various sites along the tricuspid ring. On the other hand, left-sided decrementally conducting accessory pathways are very rare. Mahaim type atrioventricular pathways were never found in the coronary sinus. The bidirectional decremental conduction properties and in particular the anatomic site of the atrioventricular accessory pathway we describe in the present report are both very interesting findings.

Radiofrequency catheter ablation of atrio-ventricular accessory pathways

Radiofrequency catheter ablation of accessory pathways may represent the treatment of choice for patients with symptomatic atrio-ventricular reentrant tachycardia or atrial fibrillation and a high ventricular response through the accessory pathways with short antegrade refractory period. Moreover, catheter ablation has contributed towards understanding anatomical and electrophysiological characteristics of accessory pathways. As far as anatomical characteristics accessory pathways may be classified into fibers with proximal insertion in right or left atrium and fibers with proximal insertion in the atrio-ventricular nodal junction. As far as electrophysiological properties are concerned, accessory pathways may be differentiated into non-decremental and decremental. In non-decremental by-pass tracts (the so-called Kent bundles) the impulse can be conducted antegradely, retrogradely and in both directions. Decremental accessory pathways generally show only antegrade conduction properties (the so-called Mahaim fibers) and can be classified in long and short pathways; in particular, catheter ablation has given considerable evidence that the vast majority (but not all) of them has a proximal insertion on the tricuspid anulus (atrio-ventricular pathways) or on the atrio-ventricular node (nodo-ventricular pathways). Decremental accessory pathways with only retrograde conduction properties are involved in the so called "Permanent Junctional Reciprocating Reentrant Tachycardia".

Successful ablation of atrioventricular nodal reentry tachycardia in a patient with persistent left superior vena cava

We report the case of a patient with atrioventricular nodal reentry tachycardia associated with persistent left superior vena cava draining to a large coronary sinus. Successful ablation was performed at the level of the superior lip of the coronary sinus ostium.

Beta-blocker effects on respiratory sinus arrhythmia and baroreflex gain in normal subjects

STUDY OBJECTIVE

The results of studies on the effect of beta-adrenergic blockade on respiratory sinus arrhythmia (RSA) are discordant. The aim of this study was to verify whether chronic beta-adrenergic blockade is capable of increasing RSA, and therefore vagal outflow, and to analyze whether the mechanism of action is central or peripheral.

PARTICIPANTS AND DESIGN

Twenty normal subjects (28+/-2 years old) were randomized to receive a hydrophilic (nadolol) beta-blocker, a lipophilic (metoprolol) beta-blocker, and placebo.

MEASUREMENTS

After 1 week of therapy, a spectral analysis was made of the variability in heart rate and systolic BP during controlled breathing at 16 breaths/min. The high-frequency component was calculated for the RR interval (measure of RSA) and systolic pressure, and the squared coherence and phase functions were assessed between RR and systolic pressure fluctuations in the respiratory band; a negative phase means that RR changes follow systolic pressure changes. The gain in the relationship between the two signal fluctuations was also calculated.

RESULTS

Both beta-blockers increased the mean (+/-SD) RR interval (placebo=808+/-21, nadolol=1,054+/-30, metoprolol=1,031+/-27 ms; p<0.0001), RSA (placebo=542, nadolol=1,177, metoprolol=1,316 ms2; p=0.002), and the gain (placebo=13.6+/-1.5, nadolol=21.9+/-2.8, metoprolol=24.5+/-3.6 ms/mm Hg; p<0.002), and both modified the phase function (placebo=-21.1+/-5.3, nadolol=-1.8+/-4.9, metoprolol=-2.9+/-4.2 degree; p<0.0001). No difference was found between nadolol and metoprolol.

CONCLUSIONS

Chronic beta-adrenergic blockade enhanced both RSA and baroreflex gain and reduced the phase between the RR interval and systolic pressure oscillations. Since no difference was found between the hydrophilic and the lipophilic beta-blockers, these changes seem to be due to a peripheral effect.

[Double-blind randomized placebo-controlled study of the effects of slow release and immediate release forms of propafenone in patients ventricular extrasystole symptoms]

This is a multicenter, randomized, double-blind, placebo-controlled, cross-over and double-dummy study aimed at testing the efficacy and tolerability of two slow-release propafenone (Pr SR) preparations and compare them with the effect of instant release propafenone (Pr IR). The study was performed in 83 patients with frequent (> 30 premature ventricular contractions/hour) and stable (< 35% variability in two 24-hour ECG monitoring periods) symptomatic premature ventricular contractions. Patients were preliminarily studied in wash-out from antiarrhythmic drugs. After a period of placebo administration, all patients underwent three consecutive periods during which they received Pr IR at the dosage of 150 mg x 3, Pr SR at the dosage of 225 mg x 2, Pr SR at the dosage of 325 mg x 2. The periods lasted 10-14 days each and the sequence was randomly assigned. Twenty-four-hour ECG monitoring periods were obtained at the end of the placebo as well as at the last day of each treatment period. Treatment efficacy was evaluated by intention to treat analysis in 80 patients and by protocol in 61. Treatment was considered efficacious when premature ventricular contraction reduction > or = 75%, couplet reduction > or = 90% and non sustained ventricular tachycardias were completely suppressed. Pr IR 150 mg x 3 was efficacious in 42% of patients, Pr SR 325 mg x 2 in 45.9% and Pr SR 225 mg x 2 in 32%. Tolerability was considered good in the majority of patients. These results show that among the different types studied, Pr SR 325 mg x 2 should be considered the treatment of choice for premature ventricular contractions.

Different trends of changes in heart rate variability in patients with anterior and inferior acute myocardial infarction

Modifications in heart rate variability (HRV) parameters occur after acute myocardial infarction. The aim of this study was to evaluate the trend of HRV change during the acute phase and the first month after myocardial infarction, and establish whether they were affected by the anterior or inferior location of the infarction. The time-domain HRV measures of 59 patients with a first uncomplicated acute myocardial infarction were computed from 24-hour ECG recordings made on days 1, 2, 10, and 28 after hospital admission. At day 1, the mean RR cycle length (NN), the standard deviation of the NN intervals (SDNN), and the root mean square successive difference of NN intervals (RMSSD) were lower in the patients with anterior myocardial infarction. Although the parameters were similar in all of the patients at day 28, their behavior over time was different (P = 0.01): the SDNN in the patients with inferior myocardial infarction had decreased to the values found in anterior myocardial infarction patients by day 2 but, at day 10, both NN and SDNN tended to recover in both groups; RMSSD had diminished in both groups by day 2, but at day 10, had increased in the patients with anterior, but not in those with inferior myocardial infarction. These findings suggest that (1) in the very early phase of myocardial infarction, HRV is different in the two locations, (2) during the first hours of myocardial infarction patients with inferior location showed a greater vagal activity than patients with anterior location that became lower at day 10, and (3) the recovery of HRV is an early phenomenon in both groups, being already evident by the second week after myocardial infarction.

Effect of respiratory rate on the relationships between RR interval and systolic blood pressure fluctuations: a frequency-dependent phenomenon

OBJECTIVE

The aims of this study were to determine the relationships between oscillations in systolic blood pressure and heart period at different breathing frequencies and to investigate the role of sympathetic contribution to this relationship.

METHODS

Fourteen healthy volunteers underwent three randomized periods of controlled breathing at 6, 10 and 16 breaths/min. ECG (RR), respiratory signal (RESP) and systolic blood pressure (SBP) were continuously recorded. The component of RR and SBP oscillations related to respiration (RRResp and SBPResp) was defined by means of uni- and bivariate spectral analysis. The squared coherence (K2) and phase between RR and RESP, and RR and SBP (RR-SBP) were also assessed. When the K2 of RR-SBP in the respiratory band was > 0.5, we considered the phase and calculated the closed-loop gain between the two signals. Seven subjects were also studied after chronic metoprolol treatment.

RESULTS

Although the mean values of RR and SBP did not differ between the three periods of breathing, the higher the respiratory rate, the smaller the RRResp and SBPResp. The phase was always negative (SBPResp changes preceded RRResp changes), thus suggesting a baroreflex link. The higher the respiratory rate, the lower the gain and phase. Pharmacological beta-adrenoceptor blockade increased the gain and shifted the phase, but the relationships found at baseline between the respiratory rate and both the gain and phase remained unchanged.

CONCLUSIONS

The effect of breath rate on the relationship between heart rate and systolic pressure variabilities is a frequency-dependent phenomenon that is also independent of the sympathetic drive.

Comparison between noninvasive indices of baroreceptor sensitivity and the phenylephrine method in post-myocardial infarction patients

BACKGROUND

Depressed baroreflex sensitivity obtained by means of a phenylephrine test plays a prognostic role in patients with a previous myocardial infarction. Our purpose was to evaluate the correlation and agreement between the baroreflex sensitivity obtained with phenylephrine and that obtained by two noninvasive methods: the alpha-index and sequence analysis.

METHODS AND RESULTS

The alpha-index was measured by means of the spectral analysis of RR and systolic blood pressure variabilities in both the high- and low-frequency bands; sequences were identified from simultaneously recorded time series in which the RR and systolic blood pressure concurrently increased or decreased. Noninvasive baroreflex sensitivity tests were performed during both spontaneous and controlled respiration. Fifty-two consecutive patients with recent myocardial infarction underwent the analyses. Although the correlations between phenylephrine and either of the noninvasive methods were always significant, those found during controlled respiration had the highest r values (r=.70). However, the limits of agreement calculated by means of the Bland and Altman method were wide for both noninvasive methods.

CONCLUSIONS

The results obtained by means of noninvasive baroreflex sensitivity assessments should not be used in clinical practice as an alternative to those obtained by the phenylephrine method.

Percent achieved of predicted peak exercise oxygen uptake and kinetics of recovery of oxygen uptake after exercise for risk stratification in chronic heart failure

To investigate whether percent achieved of predicted peak exercise oxygen uptake (%VO2max) and recovery of oxygen consumption after exercise may provide prognostic information in chronic heart failure (CHF), we prospectively studied 196 patients with mild to moderate CHF. The following variables were examined: age, etiology of CHF, functional class, ejection fraction (EF), peak exercise oxygen uptake normalized for body weight (VO2max), %VO2max, time to reach 50% of the peak oxygen uptake after exercise (T1/2VO2max), presence of nonsustained ventricular tachycardia (NSVT) and inability to take ACE-inhibitors. VO2max was the most powerful predictor of cardiac death (P<0.0001). Other independent predictors of death were EF, T1/2VO2max, NSVT and inability to take ACE-inhibitors. The discriminatory accuracy of VO2max for cardiac death was not significantly greater than that of %VO2max. In conclusion, the determination of %VO2max does not enhance risk stratification in CHF whereas the kinetics of oxygen consumption after exercise can provide prognostic information.

Assessment of cardiac vagal activity in patients with hyperthyroidism

Previous studies suggested that in patients with hyperthyroidism an autonomic imbalance and in particular a lower than normal vagal activity might be present. To verify this hypothesis we have evaluated the respiratory sinus arrhythmia (RSA, a measure of cardiac vagal activity) in ten hyperthyroid patients and in ten normal subjects. RSA was calculated from the power of the spectral component of the heart rate variability in high frequency band (HF-RR) during both spontaneous (supine and passive head-up tilt) and controlled breathing (supine). During controlled breathing the phase relation between heart rate and respiratory has been computed. The hyperthyroid patients showed a higher heart rate in all three conditions (P<0.001) and higher spontaneous respiratory rate in supine position (centered frequency of HF-RR: 0.342+/-0.015 vs 0.262+/-0.016 Hz; P<0.001). No difference was found in hyperthyroid patients compared to controls in terms of the HF-RR power in normalized units both during spontaneous breathing (supine, 43+/-8.3 vs 39.7+/-6.7%; tilt 18.8+/-5.9 vs 19.3 vs 4.1%; mean+/-SE) and controlled breathing (45.4+/-7.1 vs 48.9+/-6.9%). No difference was found also in terms of the phase relationship between the heart rate and the respiratory signals (77.5+/-32.3 vs 77.5+/-28.1, degrees). Hyperthyroid patients seem not to have an impaired cardiac vagal activity.

Effects of hydrophilic and lipophilic beta-blockers on heart rate variability and baroreflex sensitivity in normal subjects

To evaluate the effect of a hydrophilic and a lipophilic beta-blocker on the autonomic nervous system, 20 normal subjects were studied under baseline conditions and 7 days after being randomly assigned to metoprolol (200 mg/day), nadolol (80 mg/day), and placebo. Under each condition, the time-domain parameters were analyzed by means of 24-hour ECG monitoring and the frequency-domain parameters by means of the autoregressive method using 10-minute ECGs during rest, controlled respiration, and after a head-up tilt test. The alpha index (the gain in the relationship between the RR period and systolic arterial pressure variability) was also calculated. Both nadolol and metoprolol significantly increased all of the time-domain parameters except the standard deviation of the RH intervals; they also modified the frequency-domain parameters. Both blunted the significant reduction in the high frequency (HF) component and alpha index during tilt. In normal subjects, hydrophilic and lipophilic beta-blockers similarly modify the time- and frequency-domain parameters that are particularly evident when high sympathetic tone is present (during daytime and tilt). The value of the alpha index was increased by both beta-blockers in the HF, but not in the low frequency band; this difference might be due to the fact that the former is a measure of the vagal component of the baroreflex control and the latter a measure of the sympathetic component. The effects of hydrophilic and lipophilic beta-blockers on the time- and frequency-domain parameters of heart rate variability are similar.

Effects of atrial pacing stress test on ultrasonic integrated backscatter cyclic variations in normal subjects and in patients with coronary artery disease

AIMS

To evaluate the effects of acute, atrial pacing-induced, reversible myocardial ischaemia on myocardial thickening and integrated backscatter cyclic variations in patients with or without coronary artery disease.

METHODS AND RESULTS

Thirty-six patients with suspected coronary artery disease underwent transoesophageal echocardiography with simultaneous atrial pacing, and coronary angiography. In myocardial segments not related to a significantly narrowed coronary artery, both from patients with and without coronary artery disease, thickening and integrated backscatter cyclic variations were not reduced at peak pacing. In segments related to a significantly narrowed coronary artery, thickening decreased at peak pacing, was still reduced at pacing interruption and recovered at 2 min, while backscatter cyclic variations, blunted at peak pacing, immediately recovered after pacing interruption.

CONCLUSION

During stress-induced myocardial ischaemia, backscatter cyclic variations are blunted and thickening reduced. Returning to baseline, pre-atrial pacing values occur more rapidly in backscatter cyclic variations than when thickening takes place. Evaluation of stress-induced alterations in backscatter cyclic variations may aid in the identification of ischaemia-induced regional left ventricular functional impairment and, hence, in coronary artery disease diagnosis.

Heart rate dependency of premature ventricular contractions. Correlation between electrocardiographic monitoring and exercise-related patterns

AIMS

The identification of the response of ventricular arrhythmias to exercise testing could provide important information in the clinical setting but is difficult to obtain as no definite criteria are available. The aim of this study was to evaluate whether analysis of spontaneous heart rate dependency of premature ventricular contractions evaluated by means of 24 h electrocardiographic monitoring is capable of predicting their behaviour during exercise.

METHODS AND RESULTS

One hundred and twenty-six patients (49 +/- 16 years) with frequent (> 30 h) premature ventricular contractions underwent 24 h electrocardiographic monitoring in order to evaluate the relationship between arrhythmias and heart rate, and an exercise test in order to evaluate the behaviour of the arrhythmias. On the basis of the incidence of premature ventricular contractions at different cardiac cycle lengths found at electrocardiographic monitoring, three groups of patients were identified: 34 with a tachycardia-enhanced pattern (the shorter the cycle length the higher the incidence of arrhythmias); 32 with a bradycardia-enhanced pattern (the longer the cycle length the higher the incidence of arrhythmias); and 60 patients with an indifferent pattern (no relationship). During the exercise test, the number of premature ventricular contractions/min at maximal effort in comparison with baseline increased in patients with a tachycardia-enhanced pattern (couplets or runs appeared in 10), decreased in those with a bradycardia-enhanced pattern and did not change in those with an indifferent pattern. The positive predictive accuracy of the tachycardia-enhanced pattern in predicting an increase in premature ventricular contractions > 100% at maximal effort was 78%.

CONCLUSION

Identification of spontaneous behaviour between the incidence of premature ventricular contractions and the length of the preceding cardiac cycle may predict the behaviour of arrhythmias during exercise.

[Value of peak oxygen consumption during exercise for the prognostic stratification of patients with severe systolic dysfunction of the left ventricle]

We sought to assess the prognostic value of peak exercise oxygen consumption (peak VO2) in patients with severe left ventricular systolic dysfunction and mild to moderate symptoms of chronic heart failure. We focused on 1-year mortality. We prospectively studied 77 patients with left ventricular ejection fraction (EF) < or = 25% and NYHA functional class I/II (61%) or III (39%). All patients underwent cardiopulmonary exercise test, two-dimensional echocardiography and 24-hour Holter monitoring. Examined variables were age, etiology, NYHA functional class, EF, peak VO2, and presence of nonsustained ventricular tachycardia. Overall 1-year mortality rate was 23%. At univariate analysis, age > or = 60 years, ischemic etiology, and peak VO2 < 14 ml/kg/min were significantly associated with mortality. At multivariate analysis, peak VO2 was the most powerful predictor of death (p = 0.0001). In the subgroup of patients with a peak VO2 < 14 ml/kg/min, the actuarial 1-year mortality rate was 56%. One additional patient underwent heart transplantation because of severe hemodynamic deterioration. By contrast, in the subgroup of patient with a peak VO2 > 14 ml/kg/min, 1-year mortality rate was 11%. This study provides evidence that patients with severe left ventricular dysfunction and mild to moderate symptoms of chronic heart failure can be accurately stratified into subgroups with strikingly divergent prognosis by an objective criteria such as peak VO2.

Multiplane transesophageal echocardiography to detect effectiveness of selective pulmonary recombinant tissue-type plasminogen activator thrombolysis in pulmonary embolism and patent foramen ovale

A functionally patent foramen ovale can create a relevant right-to-left shunt during massive pulmonary embolism. This associated feature, although maintaining adequate cardiac output, may explain both the paradoxic embolism and the uneffectiveness of peripherally administered drugs. This case demonstrates the potential of transesophageal echocardiography in monitoring the hemodynamic findings of such patients and, consequently, the effectiveness of thrombolytic treatment.