Impaired left ventricular filling in hypertensive left ventricular hypertrophy as a marker of the presence of an arrhythmogenic substrate

Losartan controlled blood pressure and reduced left ventricular hypertrophy but did not alter arrhythmias in hypertensive men with preserved systolic function

The effect of antihypertensive therapy on arrhythmias is controversial. An initial study in patients with chronic heart failure indicated that losartan, an angiotensin II receptor antagonist, may possess antiarrhythmic properties. However, the effect of AT1 receptor antagonists on arrhythmias of subjects with good systolic function has never been evaluated. Thirty-nine men with primary hypertension (18 without left ventricular hypertrophy [LVH], and 21 with LVH, aged 48.2 +/-8.6 and 50.5 +/-6.0 years, respectively), 15 healthy normotensive subjects (47.9 +/-8.5 years), and 14 highly trained athletes (34.1 +/-1.6 years) were studied. Transthoracic echocardiography and 24-hour Holter ambulatory monitoring were performed at baseline (without treatment). Hypertensive patients underwent the same examinations after 8 months of losartan administration. The prevalence and complexity of ventricular arrhythmias, and the frequency of supraventricular arrhythmias were increased in hypertensive patients with LVH compared to normotensive controls and athletes, at baseline. A similar significant reduction of blood pressure (BP) was noted in both groups of patients (p < 0.001). The LVH was reduced in hypertensives with LVH (the left ventricular mass index by 12%, the interventricular septum by 8.1%, the posterior wall by 7%, all p < 0.01). However, the arrhythmias did not change in either group of patients, even if all hypertensives were considered as 1 group. In conclusion, an 8-month course with losartan was effective in lowering BP and reducing LVH. However, the increased arrhythmias, which were registered in hypertensive patients with LVH at baseline, did not change.

Digitized QT dispersion by the Valsalva maneuver in hypertensive patients

BACKGROUND

Hypertension is an important risk factor for sudden cardiac death, of which the incidence increases with increases in blood pressure. Prolonged QT dispersion has been identified to indicate increased risk of life-threatening ventricular arrhythmia and sudden cardiac death. In this study, QT dispersion was investigated in hypertensive patients during the strain phase of the Valsalva maneuver.

METHODS

The study population included 75 subjects: 25 with normal blood pressure (Control), 25 with stage I hypertension (Group A), and 25 with stage II hypertension (Group B). Electrocardiography for QT dispersion was recorded at 25 mm/sec paper speeds before and during the Valsalva maneuver.

RESULTS

The patients in Group B were significantly older than the controls (p<0.05). Differences in sex, smoking, diabetes, angina, and hyperlipidemia were not statistically significant between the three groups. The basal QT dispersion was 25.3 +/- 18.3 ms in the controls, 39.0 +/- 17.8 ms in Group A, and 36.8 +/- 18.8 ms in Group B. The QT dispersion was significantly higher in group A patients than the controls (p<0.05). In Group B only, a significant increase in QT dispersion was observed during the Valsalva maneuver, compared to conditions prior to the Valsalva maneuver (p<0.05).

CONCLUSION

The conditions that increase intrathoracic pressure may increase QT dispersion and severe hypertensive patients should avoid these conditions.

Markers of electrical instability in hypertensive patients with and without ventricular arrhythmias. Are they useful in identifying patients with different risk profiles?

BACKGROUND

Markers of electrical instability of the ventricular myocardium, namely abnormal repolarization and late potentials, are frequently observed in patients with hypertension when both ventricular arrhythmias and left ventricular hypertrophy are present. This information cannot be extrapolated to the population of hypertensive patients with ventricular arrhythmias but without left ventricular hypertrophy.

OBJECTIVE

To evaluate QT duration, QT dispersion and the incidence of ventricular late potentials in patients with essential hypertension, already on anti-hypertensive therapy, both with and without non-sustained ventricular arrhythmia.

DESIGN

The study population consisted of 49 patients with essential hypertension who were compared to 89 control normotensive subjects both with and without frequent (> 30 per h) ventricular ectopic beats (VPBs). Patients were divided into four groups: (1) hypertensive patients without VPBs (H, n = 19), (2) hypertensive patients with VPBs (HA, n = 30), (3) normotensive subjects without VPBs (C, n = 28), and (4) normotensive subjects with VPBs (CA, n=61).

METHODS

Echocardiographic parameters, QT interval, QT dispersion and signal-averaged ECG were evaluated without withdrawing anti-hypertensive drugs.

RESULTS

In no case was left ventricular hypertrophy documented. The number of VPBs during 24 h Holter recording (median 11 343 versus 7617) and the incidence of repetitive VPBs (37 versus 46% of patients) were similar in the two groups of patients (HA versus CA). Signal-averaged ECG parameters were normal and not different between the four groups. QT interval was longer in hypertensive patients compared to controls irrespective of the presence of VPBs. QT dispersion was slightly greater in subjects with VPBs, both hypertensive and normotensive, compared to subjects without arrhythmias.

CONCLUSIONS

In patients with hypertension well-controlled by drug therapy and without left ventricular hypertrophy, frequent VPBs are not associated with markers indicating an electrophysiological substrate for re-entrant arrhythmias. However, QT prolongation suggests the persistence of a higher risk of cardiovascular mortality that is independent of the presence of VPBs.

QT intervals and heart rate variability in hypertensive patients

Low heart rate variability and increased QT dispersion are risk factors for cardiac mortality in various patient populations. We studied dispersion of QT interval, i.e. an index of inhomogeneity of repolarization, and heart rate variability (HRV) i.e., a measure of cardiac autonomic modulation in 76 essential hypertension cases (45 women, 53.0 +/- 11.1 years, body mass index: 25.1 +/- 1.4 kg/m2) and 70 healthy cases (42 women, 54.0 +/- 10.2 years, body mass index: 25.5 +/- 1.6 kg/m2, p > 0.05). QT-corrected QT intervals and their dispersions were significantly higher in the hypertensive group (p < 0.0001), all showing a direct relation with the level of systolic and diastolic blood pressures, ventricular mass index and high Lown grade ventricular rhythm problems. Time domain measures like standard deviation of RR intervals, standard deviation of the means of all corrected RR intervals calculated at 5 min intervals (p < 0.0001), proportion of adjacent RR intervals differing by > 50 msec (p = 0.005), HRV triangular index (p = 0.007), the square root of the mean squared differences of successive RR intervals (p = 0.011), and the high frequency (HF, 0.16-0.40 Hz, p < 0.0001) part of the frequency domain measure of HRV were all decreased, whereas the low frequency (LF, 0.04-0.15 Hz, p = 0.013) part of the frequency domain measures and LF / HF ratio (p < 0.0001) were increased in hypertensive cases. Time domain and the HF part of frequency domain measures of heart rate variability showed an inverse relation with the increased levels of both systolic and diastolic blood pressures and Lown grading system of ventricular rhythm problems, whereas LF and LF / HF showed direct relations with high levels of systolic and diastolic blood pressures and high Lown grade ventricular rhythm problems. The measures of heart rate variability apart from LF and LF / HF were inversely related with the QT intervals and dispersions, whereas LF / HF was directly related with them. Therefore, we conclude that the levels of both systolic and diastolic blood pressures are related to the generation of ventricular rhythm problems either via increasing left ventricular mass which results in an increase in QT parameter measurements, or by altering heart rate variability measures indicating a disturbance in cardiac autonomic balance in essential hypertension.

Relevance of heart rate as a risk factor in hypertension

Numerous studies have shown that resting heart rate is closely correlated with blood pressure and that it is prospectively related to the development of hypertension. Moreover, there is mounting evidence to indicate that a high heart rate is associated with increased cardiovascular morbidity and mortality. In this respect, heart rate can be considered both as a marker of risk and as an independent factor in the induction of risk. Sympathetic overactivity seems to be responsible for the increase in blood pressure and hematocrit, and for the metabolic abnormalities often observed in subjects with tachycardia. Experimental studies in monkeys have shown that heart rate can also exert a direct atherogenic action on the arteries through increased wall stress. Furthermore, tachycardia can favor the occurrence of ventricular arrhythmias and sudden death. Reduction of heart rate appears to be a reasonable additional goal of antihypertensive therapy, especially in subjects with increased sympathetic tone. Nondihydropyridine calcium antagonists and drugs with agonistic properties at the I1-imidazoline receptors of the rostral ventrolateral medulla may be drugs of choice for this purpose, but whether they offer a significant morbidity-mortality advantage must be proven in prospective trials.

Heart rate as a risk factor for atherosclerosis and cardiovascular mortality: the effect of antihypertensive drugs

The aim of this review is to highlight the importance of heart rate (HR) as a risk factor for cardiovascular disease, and to discuss the classes of drugs which can be potentially useful in clinical conditions in which an elevated HR may be present. Numerous studies have shown that high resting HR is prospectively related to the development of atherosclerosis and of cardiovascular events. This relationship was independent of other major risk factors for atherosclerosis and was observed in the general population, in elderly people, in hypertensive cohorts and in patients with myocardial infarction or heart failure. The clustering of several risk factors in individuals with fast heart rate may explain why cardiovascular morbidity is higher in individuals with tachycardia. Sympathetic overactivity seems to be responsible for both the increase in HR, blood pressure and the metabolic abnormalities. Experimental studies in monkeys have shown that HR can also exert a direct atherogenetic action on the arteries through increased wall stress. Moreover, tachycardia can favour the occurrence of ventricular arrhythmias and sudden death. Reduction of HR appears as an additional goal of antihypertensive therapy. If fast HR in hypertension is a marker of increased sympathetic tone, agents which decrease HR through a decline of sympathetic outflow should be particularly efficacious. Beta-blockers retard the development of coronary atherosclerosis in cholesterol-fed monkeys and have proven to be beneficial in patients with myocardial infarction or with heart failure, but their efficacy appear limited in hypertension, probably on account of their unfavourable metabolic profile. Phenylalkylamines are devoid of this untoward effect, and seem to act also through inhibition of sympathetic discharge from the CNS. Mibefradil, a more recent calcium antagonist that selectively blocks voltage-dependent T-type calcium channels decreases HR without affecting left ventricular contractility. New drugs with agonistic properties at the I1-imidazoline receptors of the rostral ventrolateral medulla are effective in reducing blood pressure and HR by inhibiting the sympathetic outflow and improved metabolic parameters in obese or fructose-fed rats. The goal of antihypertensive therapy in the future will be to prevent or reverse those functional abnormalities which accompany the hypertensive condition. In patients with tachycardia the reduction of HR appears a desirable additional goal of therapy.

Lack of correlation between ventricular late potentials and left ventricular mass in top-level male athletes

PURPOSE

The aim of this study was to establish: 1) the prevalence of abnormal signal-averaged electrocardiogram (SAECG) in a large population of top-level athletes and 2) the relationship between SAECG parameters and left ventricular mass. One-hundred and fifty-three elite male athletes without apparent heart disease, symptoms, or arrhythmias were studied.

METHODS

Fifty-six athletes (37%) had increased left ventricular mass (> 134 g.m(-2)). All athletes underwent time-domain SAECG on 300-400 heart beats recorded at rest from three bipolar orthogonal tests with a filter setting of 40-250 Hz. Criteria for abnormality were 1) filtered QRS duration > 114 ms, 2) duration of low-amplitude signals > 38 ms, or 3) root mean square voltage of the last 40 ms of the filtered QRS < 20 microV.

RESULTS

The prevalence of abnormal SAECG was 7.2% (abnormality of one parameter), 6.5% (abnormality of two parameters), and 5.8%(abnormality of three parameters). The prevalence of abnormal SAECG was similar in athletes with or without increased left ventricular mass.

CONCLUSIONS

In conclusion, this study showed: 1) the low rate of positive results of SAECG parameters in top-level male athletes, similar to that found in healthy sedentary subjects; and 2) the lack of correlation between left ventricular mass and overall SAECG parameters.

White-coat hypertension: a selection bias? Harvest Study Investigators. Hypertension and Ambulatory Recording Venetia Study

BACKGROUND

Results of several studies have shown that subjects with white-coat hypertension (WCH) have more target-organ damage than do normotensive controls with similar ambulatory blood pressures.

OBJECTIVE

To investigate whether this is due to a selection bias.

SETTING

Seventeen hypertension clinics in northeast Italy.

MAIN OUTCOME MEASURES

Echocardiographic data in relation to WCH status.

PATIENTS AND METHODS

Mild hypertensive subjects from the HARVEST (n = 565) who underwent two ambulatory blood pressure monitorings 3 months apart and M-mode echocardiography, and 95 normotensive control subjects.

RESULTS

From first ambulatory monitoring, 90 hypertensive subjects were classified as having WCH (mean daytime blood pressure < 130/80 mmHg). Their 24 h blood pressure was similar to that of the normotensive subjects, but their left ventricular mass index was greater. From second ambulatory monitoring, only 38 of the 90 subjects still had WCH, whereas 24 h blood pressure in the other 52 had risen beyond the limit of WCH. Left ventricular mass index (89.2 +/- 2.4 g/m2), wall thickness (18.1 +/- 0.3 mm), and relative wall thickness (0.359 +/- 0.006%) of the 38 subjects with WCH at both recordings were still greater than those of the normotensive subjects (82.4 +/- 1.5 g/m2, P = 0.02; 17.2 +/- 0.2 mm, P = 0.002; and 0.337 +/- 0.004%, P = 0.025) and similar to those of the 52 subjects who no longer had WCH (88.5 +/- 2.0 g/m2, 18.7 +/- 0.2 mm, and 0.375 +/- 0.005%, all NS).

CONCLUSIONS

Owing to regression toward the mean, over 50% of the subjects with WCH could no longer be classified as such from repeated ambulatory monitoring, indicating that the current diagnosis of WCH is subject to selection bias. Cardiac remodeling was present also in the subjects confirmed to have WCH by repeated blood pressure recording, suggesting that the effect of WCH has an actual impact on target organs.

Ventricular arrhythmias in adult aortic stenosis: prevalence, mechanisms, and clinical relevance

With the longer life expectancy of the population, calcific aortic stenosis has become a common cardiac problem in the elderly. When patients with moderate to severe aortic stenosis become symptomatic, the prognosis is usually poor in absence of valve replacement and sudden death is a feared complication. It has been hypothesized that malignant ventricular arrhythmias could be responsible for the high incidence of sudden death in symptomatic patients with aortic stenosis. The purpose of this review is to analyze the prevalence, the electrophysiologic mechanisms, and the possible role of ventricular arrhythmias in the development of symptoms and in the outcome of adult subjects with aortic stenosis.

Prognostic value of ventricular arrhythmias in systemic hypertension

OBJECTIVE

Hypertensive left ventricular hypertrophy is associated with an increased risk of arrhythmias and mortality. However, no clinical study has demonstrated a significant relationship between ventricular arrhythmias and mortality in systemic hypertension.

DESIGN AND METHODS

To evaluate the prognostic value of arrhythmogenic markers, we included, prospectively, 214 hypertensive patients aged (mean+/-SD) 59.1+/-12.8 years, without symptomatic coronary disease, myocardial infarction, systolic dysfunction or electrolyte disturbances. At inclusion, a 12-lead electrocardiogram (ECG) with QT dispersion calculation, a 24 h Holter ECG (204 patients) with Lown classification of ventricular arrhythmias, echocardiography (reliable in 187 patients) and a signal-averaged ECG (125 patients) with ventricular late potentials were recorded.

RESULTS

At baseline, echocardiographic left ventricular hypertrophy was found in 63 patients (33.7%). Non-sustained ventricular tachycardia (Lown class IVb) was recorded in 33 patients (16.2%) and late potentials in 27 patients (21.6%). After a mean follow-up of 42.4+/-26.8 months, all-cause mortality was 11.2% (24 patients); 17 patients died of cardiac causes (7.9%); of these, nine (4.2%) died suddenly. In univariate analysis, age, Lown class IVb and a QT dispersion > 80 ms were significantly related to global, cardiac and sudden death (P < 0.01). The left ventricular mass index was related to cardiac mortality (P= 0.002). In multivariate analysis, only Lown class IVb was an independent predictor of global and cardiac mortality, increasing the risk of global death 2.6-fold (95% confidence interval 1.2-6.0) and cardiac death 3.5-fold (95% confidence interval 1.2-9.7).

CONCLUSION

In hypertensive patients the presence of non-sustained ventricular tachycardia has prognostic value.

Prevalence of late potentials in adult aortic stenosis

Sudden death and syncope are well-recognized clinical manifestations of valvular aortic stenosis (AS). Furthermore, patients with left ventricular hypertrophy due to hypertension have a greater prevalence of late potentials (LP) compared with normal subjects. Chronic pressure overload in AS is frequently characterized by development of left ventricular hypertrophy. The aims of this study were (1) to determine the prevalence of LP in patients with moderate to severe AS, and (2) to investigate the relationship between LP and left ventricular hypertrophy. Signal-averaged electrocardiograms (SAECG) were recorded using a 40 Hz high pass filter in 32 patients (19 M and 13 F), aged 69 +/- 11 years with AS, and in 25 age- and sex-matched controls. QRS duration (QRSD) < 114 ms, low amplitude signal of last 40 ms (LAS40) < 38 ms and root mean square voltage of last 40 ms (RMS40) > 20 microV were considered normal. LP were considered to be present if at least two of the above criteria were abnormal. Each patient underwent a complete echo-Doppler examination and the following parameters were measured; aortic valve area, fractional shortening, left ventricular end-diastolic diameter and mass index. Coronary arteriography was performed in 17 (53%) patients. LP were present in 8 out of 32 (25%) AS patients and in 1 out of 25 controls (4%); this difference was statistically significant (P < 0.006). No difference with regard to age, sex, presence of congestive heart failure, angina, syncope, complex ventricular arrhythmias and coronary artery disease was found in AS patients with and without LP. No correlation was found between indices of left ventricular structure and function and each SAECG parameter. In conclusion, the prevalence of LP in patients with AS is higher than in controls and the presence of LP in AS might be related to factors other than coronary artery disease and left ventricular mass and/or function.