Heart rate variability and left ventricular diastolic function in patients with borderline hypertension with and without left ventricular hypertrophy

Informative Nature and Nonlinearity of Lagged Poincaré Plots Indices in Analysis of Heart Rate Variability

Lagged Poincaré plots have been successful in characterizing abnormal cardiac function. However, the current research practices do not favour any specific lag of Poincaré plots, thus complicating the comparison of results of different researchers in their analysis of heart rate of healthy subjects and patients. We researched the informative nature of lagged Poincaré plots in different states of the autonomic nervous system. It was tested in three models: different age groups, groups with different balance of autonomous regulation, and in hypertensive patients. Correlation analysis shows that for lag l = 6, SD1/SD2 has weak (r = 0.33) correlation with linear parameters of heart rate variability (HRV). For l more than 6 it displays even less correlation with linear parameters, but the changes in SD1/SD2 become statistically insignificant. Secondly, surrogate data tests show that the real SD1/SD2 is statistically different from its surrogate value and the conclusion could be made that the heart rhythm has nonlinear properties. Thirdly, the three models showed that for different functional states of the autonomic nervous system (ANS), SD1/SD2 ratio varied only for lags l = 5 and 6. All of this allow to us to give cautious recommendation to use SD1/SD2 with lags 5 and 6 as a nonlinear characteristic of HRV. The received data could be used as the basis for continuing the research in standardisation of nonlinear analytic methods.

Heart rate variability and renal organ damage in hypertensive patients

Heart rate variability (HRV), a noninvasive measure of autonomic dysfunction and a risk factor for cardiovascular disease (CVD), has not been systematically studied in hypertensive patients in relation with renal involvement. A retrospective analysis on a cohort of hypertensive patients was performed to show differences in groups of patients categorized according to renal involvement, assessed by glomerular filtration rate (GFR). Patient with 24-h ECG Holter monitoring and other clinical information registered in the database of the Hypertension Clinic of the University of Naples Federico II were selected. Linear standard HRV measures were computed according to international guidelines on 24-h nominal ECG. A total of 200 patients were included in the present study. Decreased ratio of low to high frequency power (LF/HF) was associated with patient with moderate GFR, the highest grade of renal involvement considered in this study. These results were consistent with the findings of previous studies which concluded that depressed HRV was associated with higher risk of progression to end-stage renal disease and suggested that autonomic dysfunction may lead to kidney damage. Further research is needed to define the role of autonomic dysfunction in the development of renal disease and of HRV as a diagnostic or prognostic maker in hypertensive patients.

Heart rate variability and target organ damage in hypertensive patients

Background

We evaluated the association between linear standard Heart Rate Variability (HRV) measures and vascular, renal and cardiac target organ damage (TOD).

Methods

A retrospective analysis was performed including 200 patients registered in the Regione Campania network (aged 62.4 ± 12, male 64%). HRV analysis was performed by 24-h holter ECG. Renal damage was assessed by estimated glomerular filtration rate (eGFR), vascular damage by carotid intima-media thickness (IMT), and cardiac damage by left ventricular mass index.

Results

Significantly lower values of the ratio of low to high frequency power (LF/HF) were found in the patients with moderate or severe eGFR (p-value < 0.001). Similarly, depressed values of indexes of the overall autonomic modulation on heart were found in patients with plaque compared to those with a normal IMT (p-value <0.05). These associations remained significant after adjustment for other factors known to contribute to the development of target organ damage, such as age. Moreover, depressed LF/HF was found also in patients with left ventricular hypertrophy but this association was not significant after adjustment for other factors.

Conclusions

Depressed HRV appeared to be associated with vascular and renal TOD, suggesting the involvement of autonomic imbalance in the TOD. However, as the mechanisms by which abnormal autonomic balance may lead to TOD, and, particularly, to renal organ damage are not clearly known, further prospective studies with longitudinal design are needed to determine the association between HRV and the development of TOD.

Office and 24-hour heart rate and target organ damage in hypertensive patients

BACKGROUND

We investigated the association between heart rate and its variability with the parameters that assess vascular, renal and cardiac target organ damage.

METHODS

A cross-sectional study was performed including a consecutive sample of 360 hypertensive patients without heart rate lowering drugs (aged 56 ± 11 years, 64.2% male). Heart rate (HR) and its standard deviation (HRV) in clinical and 24-hour ambulatory monitoring were evaluated. Renal damage was assessed by glomerular filtration rate and albumin/creatinine ratio; vascular damage by carotid intima-media thickness and ankle/brachial index; and cardiac damage by the Cornell voltage-duration product and left ventricular mass index.

RESULTS

There was a positive correlation between ambulatory, but not clinical, heart rate and its standard deviation with glomerular filtration rate, and a negative correlation with carotid intima-media thickness, and night/day ratio of systolic and diastolic blood pressure. There was no correlation with albumin/creatinine ratio, ankle/brachial index, Cornell voltage-duration product or left ventricular mass index. In the multiple linear regression analysis, after adjusting for age, the association of glomerular filtration rate and intima-media thickness with ambulatory heart rate and its standard deviation was lost. According to the logistic regression analysis, the predictors of any target organ damage were age (OR = 1.034 and 1.033) and night/day systolic blood pressure ratio (OR = 1.425 and 1.512). Neither 24 HR nor 24 HRV reached statistical significance.

CONCLUSIONS

High ambulatory heart rate and its variability, but not clinical HR, are associated with decreased carotid intima-media thickness and a higher glomerular filtration rate, although this is lost after adjusting for age.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01325064.

Reduced bone mineral density in hypertensive patients is associated with left ventricular diastolic dysfunction, not left ventricular hypertrophy

Left ventricular (LV) hypertrophy and diastolic dysfunction are commonly observed in hypertensive patients, and have been demonstrated to be risk factors of chronic heart failure due to LV diastolic dysfunction. Recently, reduced bone mineral density has been found in hypertensive patients compared with healthy controls. However, relationships between bone mineral density and LV hypertrophy and diastolic dysfunction have not been fully assessed. We examined relationships between bone mineral density and both LV hypertrophy and diastolic dysfunction in 38 hypertensive patients (23 males, 15 females; mean age 71 ± 8 y) who had been treated with antihypertensive drugs for at least 1 year. The bone mineral density of the calcaneus was measured with a quantitative ultrasound measurement device (A-1000 EXPRESS/InSight, GE Healthcare, Horten, Norway), and the stiffness index was determined as a parameter of bone mineral density. Echocardiography was performed to measure the left ventricular mass index as a parameter of LV hypertrophy. Left ventricular diastolic dysfunction was also assessed by early diastolic mitral annular velocity (e'), and the ratio of early transmitral flow velocity (E) to e' (E/e'). The bone mineral density did not correlate with left ventricular mass index, but did correlate with e' (r = 0.453, P < .01) and E/e' (r = -0.359, P < .05). Thus, reduced bone mineral density in hypertensive patients is not associated with LV hypertrophy but with LV diastolic dysfunction. Hypertensive patients with reduced bone mineral density may have a high risk of chronic heart failure due to LV diastolic dysfunction as well as bone fractures due to osteoporosis.

Cardiac and vascular consequences of pre-hypertension in youth

Hypertension is associated with increased left ventricular mass (LVM) and carotid intima-media thickness (cIMT), which predict cardiovascular (CV) events in adults. Whether target organ damage is found in pre-hypertensive youth is not known. The authors measured body mass index, blood pressure, fasting glucose, insulin, lipids and C-reactive protein, LVM/height(2.7) (LVM index), diastolic function, cIMT, carotid stiffness, augmentation index, brachial artery distensibility, and pulse wave velocity (PWV) in 723 patients aged 10 to 23 years (29% with type 2 diabetes mellitus). Patients were stratified by blood pressure level (normotensive: 531, pre-hypertensive: 65, hypertensive: 127). Adiposity and CV risk factors worsened across blood pressure group. There was a graded increase in cIMT, arterial stiffness, and LVM index and decrease in diastolic function from normotension to pre-hypertension to hypertension. In multivariable models adjusted for CV risk factors, status as pre-hypertension or hypertension remained an independent determinant of target organ damage for LVM, diastolic function, internal cIMT, and carotid and arterial stiffness. Pre-hypertension is associated with cardiovascular target organ damage in adolescents and young adults.

Prehypertension: should we be treating with pharmacologic therapy?

Prehypertension, defined by Seventh Joint National Committee (JNC 7) as a blood pressure (BP) 120-139/80-89 mm Hg, was controversial. Approximately 31-37% of US adults are prehypertensive, and approximately 12-14% have BP of 130-139/85-89 mm Hg or ;Stage 2' prehypertension, is associated with approximately 3-fold greater likelihood of developing hypertension and roughly twice the cardiovascular events than BP <120/80 mm Hg. Lifestyle change is the only intervention recommended for most prehypertensives. When fully implemented, lifestyle changes lower BP and prevent cardiovascular events, but evidence for community-wide effectiveness is limited. The Trial of Preventing Hypertension (TROPHY) documented that angiotensin receptor blockade safely lowers BP and prevents and/or delays hypertension in Stage 2 prehypertensives. Prehypertensives with diabetes or nephropathy are at high risk and should receive antihypertensive treatment according to JNC 7. Epidemiological data suggest that the number needed to treat to prevent a cardiovascular event in these at-risk Stage 2 prehypertensives is similar to Stage 1 hypertensives when both groups have one or more concomitant risk factors. Clinical trials are urgently needed to address this question. In the absence of clinical trials data, we believe it is prudent for the concerned clinician to consider initiating antihypertensive pharmacotherapy in selected Stage 2 prehypertensive patients at significant absolute risk for progression to hypertension and cardiovascular events.

Comparison of isoproterenol and dobutamine in the induction of cardiac hypertrophy and fibrosis

Isoproterenol (Iso) was a clinical therapeutic that is now used as a research means for the induction of cardiac hypertrophy. Currently, dobutamine (Dob) has replaced Iso as the preferred inotropic β-adrenergic agent to wean patients from cardiopulmonary bypass and to sustain adequate cardiac function during the postoperative period. We sought to compare the cardiac structural and functional effects of long-term administration (7days) of Iso with Dob at a dose of 40μg/mouse/day in 12-week-old C57BL/6 female mice. Cardiac function was determined with transthoracic echo cardiography (ECHO) 24 hours after the last dose. Cardiac wet weights increased 33% and 24% in the Iso and Dob groups compared with controls ( p < 0.05). Dob and Iso significantly increased cardiac fibrosis and decreased cardiac function with chronic administration. Administration also resulted in increased left atrial size, suggesting that both Dob and Iso decreased LV compliance, but did not induce heart failure. In conclusion, chronic administration of Dob may have a detrimental effect on cardiac structure and function.

Cardiac hypertrophy induced by sustained β-adrenoreceptor activation: pathophysiological aspects

Cardiac hypertrophy is promoted by adrenergic over-activation and represents an independent risk factor for cardiovascular morbidity and mortality. The basic knowledge about mechanisms by which sustained adrenergic activation promotes myocardial growth, as well as understanding how structural changes in hypertrophied myocardium could affect myocardial function has been acquired from studies using an animal model of chronic systemic beta-adrenoreceptor agonist administration. Sustained beta-adrenoreceptor activation was shown to enhance the synthesis of myocardial proteins, an effect mediated via stimulation of myocardial growth factors, up-regulation of nuclear proto-oncogenes, induction of cardiac oxidative stress, as well as activation of mitogen-activated protein kinases and phosphatidylinositol 3-kinase. Sustained beta-adrenoreceptor activation contributes to impaired cardiac autonomic regulation as evidenced by blunted parasympathetically-mediated cardiovascular reflexes as well as abnormal storage of myocardial catecholamines. Catecholamine-induced cardiac hypertrophy is associated with reduced contractile responses to adrenergic agonists, an effect attributed to downregulation of myocardial beta-adrenoreceptors, uncoupling of beta-adrenoreceptors and adenylate cyclase, as well as modifications of downstream cAMP-mediated signaling. In compensated cardiac hypertrophy, these changes are associated with preserved or even enhanced basal ventricular systolic function due to increased sarcoplasmic reticulum Ca(2+) content and Ca(2+)-induced sarcoplasmic reticulum Ca(2+) release. The increased availability of Ca(2+) to maintain cardiomyocyte contraction is attributed to prolongation of the action potential due to inhibition of the transient outward potassium current as well as stimulation of the reverse mode of the Na(+)-Ca(2+) exchange. Further progression of cardiac hypertrophy towards heart failure is due to abnormalities in Ca(2+) handling, necrotic myocardial injury, and increased myocardial stiffness due to interstitial fibrosis.

Autonomic cardiovascular control and diastolic dysfunction in hypertensive subjects

BACKGROUND

Early hypertension is associated with left ventricular diastolic dysfunction due to increased end-diastolic pressure. This increase, through the cardiopulmonary reflexes, can influence autonomic cardiovascular control.

METHODS

We assessed autonomic nervous system modulation of cardiovascular signals by power spectral analysis of RR interval and systolic arterial pressure variabilities in subjects with recently diagnosed hypertension with or without diastolic dysfunction and in normotensive control subjects.

RESULTS

Both hypertensive groups had higher low-frequency (LF) power expressed in normalized units (NUs) than normotensive controls (p < 0.05; p < 0.001) during controlled breathing at rest. The LF spectral index measured after tilt was greater in hypertensive subjects with diastolic dysfunction than in those without (p < 0.05). LF NUs measured at rest correlated significantly with the E/A wave ratio and after tilt with the E-wave deceleration time.

CONCLUSIONS

These results seem to indicate that in subjects with recently diagnosed hypertension sympathetic modulation of the sinus node prevails. During tilt, a maneuver designed to stimulate systemic arterial and cardiopulmonary baroreceptor reflexes, hypertensive subjects with diastolic dysfunction, who presumably also have higher end-diastolic pressures, seem to have greater sympathetic modulation of the sinus node than hypertensive subjects without diastolic dysfunction.

Regression of Left Ventricular Hypertrophy in Diabetic Nephropathy: Loss of Parasympathetic Function Predicts Response to Treatment

Both left ventricular (LV) hypertrophy and decreased autonomic function are predictors of adverse cardiac events. Patients with diabetic nephropathy have an excess cardiovascular risk. The authors determined heart rate variability from 24-hour ambulatory electrocardiographic recordings and measures of LV mass with systolic and diastolic function from echocardiograms. Patients with diabetic nephropathy (n=16) were seen weekly for insulin and hypertension management. Glycohemoglobin decreased from 9.5+/-0.4% to 8.3+/-0.4% (p=0.01), and advanced glycated end products decreased from 12.1+/-2.2 to 7.4+/-1.2 units (p=0.03). Mean arterial pressure and body weight did not change. Serum creatinine increased (1.8+/-0.1 mg/dL to 2.0+/-0.2 mg/dL; p=0.03). The authors used a panel of markers of baseline heart rate variation to assess autonomic function. When covariance of the heart rate interval results were evaluated, the group below the median was found to have a significant decrease in LV mass, from 230 g to 184 g (p=0.013); the group above the median had an increase (182 g to 193 g; p=0.5329). Baseline covariance of the heart rate interval predicted 12-month changes in LV mass in 13 of 16 patients (predictive accuracy, 81%). Improvement in measures of heart rate variation correlated with a decrease in LV mass. Parallel improvement of LV mass and autonomic function suggests a common mechanism, allowing for prediction of LV mass improvement through analysis of baseline heart rate variation.

Circadian heart rate and blood pressure variability considered for research and patient care

OBJECTIVES

To review mechanisms of circadian variations in heart rate variability (HRV) and blood pressure variability (BPV) and mortality and morbidity due to cardiovascular diseases (CVD).

METHODS

Results from 7-day/24-h HRV and BPV are interpreted by gender and age-specified reference values in the context of a Medline search.

RESULTS

Abnormal HRV and BPV measured around the clock for 7 days provides information on the risk of subsequent morbid events in subjects without obvious heart disease and without abnormality outside the conventional (in the sense of chronobiologically unquantified) physiological range. Meditation, beta-blockers, ACE inhibitors, n-3 fatty acids and estrogens may have a beneficial influence on HRV, but there is no definitive outcome-validated therapy. Low HRV has been associated with a risk of arrhythmias and arrhythmic death, unstable angina, myocardial infarction, progression of heart failure and atherosclerosis. BPV may be characterized by treatable circadian-hyper-amplitude-tension (CHAT), which can be transient '24-h CHAT' or '7-day-CHAT', MESOR-hypertension and/or an unusually-timed (odd) circadian acrophase (ecphasia), all associated with an increased risk of stroke, stroke death, myocardial infarction, and kidney disease.

CONCLUSIONS

Precise insight into the patho-physiology in time of HRV and BPV is needed with development of a consensus on best measures of HRV for clinical purposes and to determine when a 7-day record interpreted chronobiologically suffices and when it does not, for detection within as well as outside the conventional normal range, for diagnostic clinical practice and to direct therapy of risk greater than that associated with hypertension, smoking or any other risk factor.