Elevated myocardial repolarization lability and arterial baroreflex dysfunction in healthy individuals with nondipping blood pressure pattern

Nocturnal systolic blood pressure dipping and progression of chronic kidney disease

The relationship between declining nocturnal blood pressure (BP) and adverse cardiovascular outcomes is well-recognized. However, the relationship between diurnal BP profile and the risk of chronic kidney disease (CKD) progression is unclear. Herein, we examined the association between nocturnal systolic SBP (SBP) dipping and CKD progression in 1061 participants at the Cardiovascular and Metabolic Disease Etiology Research Center-High Risk (CMERC-HI). The main exposure was diurnal systolic BP (SBP) profile and diurnal SBP difference ([nighttime SBP-daytime SBP] × 100/daytime SBP). The primary outcome was CKD progression, defined as a composite of ≥ a 50% decline in the estimated glomerular filtration rate from baseline or the initiation of kidney replacement therapy. During 4749 person-years of follow-up (median, 4.8 years), the composite outcome occurred in 380 (35.8%) participants. Compared to dippers, the hazard ratios (HRs) for the risk of adverse kidney outcomes were 1.02 (95% confidence interval [CI], 0.64-1.62), 1.30 (95% CI, 1.02-1.66), and 1.40 (95% CI, 1.03-1.90) for extreme dipper, non-dipper, and reverse dipper, respectively. In a continuous modeling, a 10% increase in diurnal SBP difference was associated with a 1.21-fold (95% CI, 1.07-1.37) higher risk of CKD progression. Thus, decreased nocturnal SBP decline was associated with adverse kidney outcomes in patients with CKD. Particularly, patients with non-dipping and reverse dipping patterns were at higher risk for CKD progression than those with a dipping pattern.

Long-term circadian disruption shortens life span and dampens blood pressure diurnal rhythms in stroke-prone spontaneously hypertensive rats

Environmental cues such as light and timing of food intake influence molecular clocks that produce circadian rhythmicity of many biological functions. The master circadian clock is entrained by light input and synchronizes with peripheral clocks in every organ of the body. Careers that require rotating shift work schedules predispose workers to a constant desynchronization of these biological clocks and are associated with increased risk of cardiovascular disease. We used a stroke-prone spontaneously hypertensive rat model exposed to a known biological desynchronizer, chronic environmental circadian disruption (ECD), to test the hypothesis that it would accelerate the time to stroke onset. We then investigated whether time-restricted feeding could delay stroke onset and evaluated its usefulness as a countermeasure when combined with the constant disruption of the light cycle. We found that phase advancing of the light schedule accelerated stroke onset. Restricting food access time to 5 h/day regardless of lighting profoundly delayed stroke onset in both standard 12-h:12-h light/dark or ECD-lighting conditions compared with ad libitum feeding; however, acceleration by ECD versus control lighting conditions was still observed. Since hypertension is a precursor to stroke in this model, we assessed blood pressure in a small cohort longitudinally using telemetry. Mean daily systolic and diastolic blood pressure increased in a similar manner across rats in control and ECD conditions, thus hypertension was not grossly accelerated to cause earlier strokes. However, we observed intermittent dampening of rhythms after each shift of the light cycle reminiscent of a relapsing-remitting nondipping state. Our results suggest that constant disruption of environmental rhythms may be associated with an increased risk of cardiovascular complications in the presence of cardiovascular risk factors.NEW & NOTEWORTHY This stroke-prone spontaneously hypertensive rat model significantly delayed stroke onset with the timed food restriction intervention. Blood pressure recordings in this same model were continuous through the 3 mo and showed dampened systolic rhythms after each shift in the lighting schedule.

Blunted circadian variation of blood pressure in individuals with neurofibromatosis type 1

BACKGROUND

Cardiovascular events such as myocardial infarction and stroke are life-threatening complications associated with Neurofibromatosis type 1 (NF1). As previous studies observed an association between cardiovascular events and the loss of circadian variations of blood pressure, we investigated the 24 h circadian rhythm of blood pressure (BP) in 24 NF1 patients (10 males and 14 females, with a mean age of 39.5 years ± 14 years) by using ambulatory blood pressure monitoring (ABPM).

RESULTS

Only one-third of the patient were dippers, 50% were non-dippers, and 17% were risers. Reduced variability of systolic and diastolic nocturnal blood pressure was observed in NF1 patients compared with several studies of normotensive individuals (p = 0.024). In NF1 patients, the blunted systolic nocturnal decline was significantly associated with the number of neurofibromas (p = 0.049) and the presence of a plexiform neurofibroma (p = 0.020).

CONCLUSIONS

Most NF1 patients in this study showed a "non-dipper" pattern with a blunted nocturnal BP decline, which is considered an independent risk factor for cardiovascular events in normotensive and hypertensive individuals. Periodic monitoring of BP should be included in NF1 follow-up guidelines to diagnose masked hypertension or a non-dipper/riser pattern which would significantly increase the morbidity and mortality of NF1 patients to implement therapeutic strategies.

The relationship between white coat hypertension and the index of cardiac electrophysiological balance (ICEB)

Aim: The index of cardiac electrophysiological balance (ICEB) is a new marker that can show the potential for ventricular arrhythmia and indicate the balancebetween ventricular depolarization and repolarization. A tendency toward ventricular arrhythmia has been shown innon-dipper hypertension and prehypertensive patients in various studies. White coat hypertension (WCH) has been shown to be associated with target organ damage and the actual development of hypertension. In this study, we aimed to evaluate the effect of dipper and non-dipper patterns on the ICEB in patients diagnosed with WCH. Material and Method: A total of 108 patients were included in this study. Patients were divided into two groups as dipper and non-dipper patterns according to ABPM. QT/QRS (ICEB) and cQT/QRS (ICEBc) were recorded with computerized interpretation of the electrocardiogram. Results: While electrocardiographic parameters including heart rate, PR interval, QT interval, cQT interval, and ICEB were similar in both groups (p>.05), in the non-dipper group, QRS duration was lower (p=.017) and ICEBc was higher (p=.001). Conclusion: ICEBc may predict asusceptibility to ventricular arrhythmias in WCH patients. Therefore, non-dipper WCH patients with a high ICEBc should be followed for arrhythmia outcomes in addition to hypertensive outcomes.

Abnormal Circadian Blood Pressure Variation is Associated with SYNTAX Scores in Hospitalized Patients with Acute Coronary Syndrome

BACKGROUND

Blunted nocturnal blood pressure (BP) reduction, referred to as non-dipper hypertension, is a strong predictor of cardiovascular morbidity and mortality.

OBJECTIVES

This study aimed to investigate the relationship between non-dipper hypertension and the severity and complexity of coronary artery disease using SYNTAX score in hospitalized patients with acute coronary syndrome.

METHODS

A total of 306 consecutive patients with acute coronary syndrome were screened. Patients who were clinically stable and admitted to the intermediate intensive care unit at least 24 hours after angiography and/or successful revascularization. After the exclusion criteria, 141 patients (34 female and 107 male; mean age 61 ± 11 years) were included. Non-dipper hypertension has been defined as a 0% to 10% decrease in average systolic BP at nighttime compared to daytime, measured at hourly intervals using the same automatic BP measuring device on bedside monitors (Vismo PVM-2701; Nihon Kohden Corp., Tokyo, Japan). SYNTAX score was calculated with an online calculator. The independent predictors of SYNTAX score were assessed using multivariable logistic regression analysis. P < 0.05 was considered statistically significant.

RESULTS

The patients with non-dipper hypertension had higher SYNTAX score than the patients with dipper hypertension (11.12 ± 6.41 versus 6.74 ± 6.45, p < 0.0001). In a multivariable logistic regression model, non-dipper hypertension status (odds ratio: 5.159; 95% confidence interval: 2.246 to 11.852, p < 0.001), sex (p = 0.012) and low-density lipoprotein cholesterol (p = 0.008) emerged as independent predictors of high SYNTAX score.

CONCLUSIONS

The results of our study provide a possible additional mechanism linking abnormal circadian BP profile with coronary artery disease severity and complexity in patients with acute coronary syndrome.

Defining the nocturnal period in 24-h ambulatory blood pressure monitoring: a comparison of three methods

OBJECTIVES

The purpose of our study was to compare three definitions of ambulatory blood pressure (BP) nocturnal period and to assess their agreement in determining nocturnal BP dipping patterns.

METHODS

We investigated 69 subjects with metabolic syndrome, aged 50-55 years. In all subjects, we assessed 24-h BP monitoring, electrocardiogram and actigraphy profiles. The nocturnal period was defined in three ways: as a fixed narrow nighttime period from 01:00 to 06:00, as a self-reported sleeping period and as a disappearance and onset of physical activity recorded by the actigraph.

RESULTS

Our study revealed a significant discrepancy between the self-reported and actigraphy-based nocturnal periods (P < 0.001). In addition, different definitions of the nighttime yielded significant differences in determining nondipping, extreme dipping and dipping BP patterns, the identification of the latter being affected the most. The actigraphy-based approach best aligned with the fixed-time determination of the nocturnal period: Cohen's kappa coefficient for the nondipping pattern was 0.78 (0.58-1), for the dipping pattern 0.75 (0.59-0.91) and for the extreme dipping pattern 0.81 (0.65-0.97). In comparison to the self-reported determination of the nocturnal period, using the actigraphy-based approach resulted in reclassifying the nocturnal BP pattern in 20.3% of subjects.

CONCLUSIONS

The lack of agreement between fixed-time, self-reported and actigraphy-based determinations of the nighttime period affects the identification of the nocturnal BP patterns. In comparison to the self-reported nocturnal period estimation, the actigraphy-based approach results in the reclassification of BP dipping status in every fifth subject.

Nighttime blood pressure decline as a predictor of renal injury in patients with hypertension: a population-based cohort study

We explored whether the nighttime blood pressure (BP) decline predicts renal function decline in a population-based cohort with primary hypertension. We measured the baseline ambulatory BP and glomerular filtration rate (GFR) in a cohort of 1,042 primary hypertensive patients. We repeated the GFR measurements and calculated the rate of GFR decline after a median follow-up of 5.8 years. The estimated GFR (eGFR) declined by -0.23 to -0.20 mL/min per year as the nighttime systolic BP (SBP), diastolic BP (DBP), and mean BP decline rates increased by 1% (P < 0.001). In the fully adjusted model, the nighttime SBP, DBP, and mean BP were all related to a steeper rate of eGFR decline by -0.25 to -0.22 mL/min per 1% increase. The adjusted multivariable results indicated that the odds of an eGFR decline were reduced by 46% when the nighttime SBP decline rate increased by 1% (OR= 0.54, 95% CI: 0.46-0.62). The restricted cubic spline model indicated a non-linear dose-response relationship with the nighttime SBP, DBP, and mean BP. Nighttime BP may be an important biomarker of renal function injury in hypertensive patients.

QTc Interval Predicts Disturbed Circadian Blood Pressure Variation

Background

The relationship between electrocardiographic evaluation and circadian blood pressure (BP) variation in young and middle-aged hypertensive patients remains unknown.

Methods

A total of 171 hypertensive patients were included in the study. First, patients were divided into a young and middle-aged group and an elderly group. The two groups were then separately classified into three subgroups on the basis of circadian variation of BP as dippers, non-dippers and reverse-dippers. The electrocardiographic evaluation was calculated from 12-lead electrocardiography (ECG).

Results

QTc intervals were shortest in the dippers and longest in the reverse-dippers in the young and middle-aged group (QTc dipper: 416.53±18.37ms; non-dipper: 438.30±29.71ms; reverse-dipper: 444.93±25.47ms; for dipper vs non-dipper, and dipper vs reverse-dipper P<0.05). QTc interval was found to be an independent risk factor for the non-dipper BP pattern (Odds ratio 1.049; 95% CI 1.01-1.089; P=0.012) and reverse-dipper BP pattern (Odds ratio 1.051; 95% CI 1.007-1.098; P=0.023) in young and middle-aged hypertensive patients. No significant differences in other ECG parameters were found among the three subgroups in the young and middle-aged group.

Conclusion

Our study suggested that QTc interval might serve as a risk factor for non-dipper BP pattern and reverse-dipper BP pattern in young and middle-aged hypertensive patients.

The relationship between fragmented QRS and non-dipper status in hypertensive patients without left ventricular hypertrophy

BACKGROUND

Fragmented QRS (fQRS) has been shown to be associated with poor outcome in various cardiovascular diseases. Non-dipper hypertension is also associated with increased cardiovascular mortality. The aim of our study is to investigate the relationship between fQRS and non-dipper status in hypertensive patients without left ventricular hypertrophy (LVH).

METHODS

This study included 106 hypertensive patients without LVH. Patients were divided into two groups: dipper hypertension and non-dipper hypertension. The presence of fQRS was analyzed from surface electrocardiography.

RESULTS

Frequency of fQRS (56% vs. 19.6%, p < 0.001) and mean number of leads with fQRS (1.9 ± 1.7 vs. 0.6 ± 1.0, p < 0.001) were significantly higher in patients with non-dipper hypertension compared to dipper hypertension. In addition, the number of leads with fQRS was positively correlated with systolic (r = 0.334, p < 0.001) and diastolic (r = 0.280, p = 0.004) blood pressures (BP). By a multivariate regression analysis, fQRS (OR: 5.207, 95% CI: 2.195-12.353, p < 0.001) was found to be independent predictor of non-dipper status.

CONCLUSION

fQRS is independent predictor of non-dipper status in hypertensive patients without LVH. Also, the higher number of leads with fQRS is associated with higher sleep systolic and diastolic BPs.

Nocturnal Non-dipping Blood Pressure Profile in Black Normotensives Is Associated with Cardiac Target Organ Damage

PURPOSE

A non-dipping pattern of nocturnal blood pressure in hypertensive patients is an established predictor of cardiovascular risk, especially in Blacks. However, data on non-dipping normotensives and cardiovascular risk in this population is sparse. In this study, we aim to determine if a non-dipping profile in a cohort of Black normotensives is associated with cardiac target organ damage.

METHODS

We studied ambulatory blood pressure patterns in 43 normotensive Black patients of Caribbean origin and classified their profiles as dippers (DP) and non-dippers (NDP) based on their nocturnal blood pressure profiles. Cardiac target organ damage was estimated from 2-D echocardiogram.

RESULTS

The mean age of the cohort was 52 years. Both groups were similar with respect to baseline age, sex, weight, height, body mass index and daytime ambulatory BP. There was a statistically significant difference in nocturnal blood pressure between DP and NDP groups (112 ± 7/64 ± 2 mm Hg vs 117 ± 3/69 ± 2 mm Hg, P=.004). The NDP cohort showed evidence of cardiovascular target damage on echocardiography with a significantly increased relative wall thickness (.35 ± .07 cm vs .42 ± .05 cm, P=.001), left ventricular mass index (95 ± 14 vs 105 ± 14 g/m(2), P=.018) and left atrial volume index (26 ± 3.5 vs. 30 ± 3.4, P=.001). Left ventricular geometry in the non-dippers also showed increased concentric remodeling, concentric and eccentric hypertrophy.

CONCLUSIONS

Our study demonstrates that nocturnal non-dipping of blood pressure in normotensive Blacks of Caribbean origin may be associated with cardiovascular end organ damage thereby providing new surveillance and therapeutic targets.

QT interval variability in body surface ECG: measurement, physiological basis, and clinical value: position statement and consensus guidance endorsed by the European Heart Rhythm Association jointly with the ESC Working Group on Cardiac Cellular Electrophysiology

This consensus guideline discusses the electrocardiographic phenomenon of beat-to-beat QT interval variability (QTV) on surface electrocardiograms. The text covers measurement principles, physiological basis, and clinical value of QTV. Technical considerations include QT interval measurement and the relation between QTV and heart rate variability. Research frontiers of QTV include understanding of QTV physiology, systematic evaluation of the link between QTV and direct measures of neural activity, modelling of the QTV dependence on the variability of other physiological variables, distinction between QTV and general T wave shape variability, and assessing of the QTV utility for guiding therapy. Increased QTV appears to be a risk marker of arrhythmic and cardiovascular death. It remains to be established whether it can guide therapy alone or in combination with other risk factors. QT interval variability has a possible role in non-invasive assessment of tonic sympathetic activity.

Prognostic Effect of the Nocturnal Blood Pressure Fall in Hypertensive Patients: The Ambulatory Blood Pressure Collaboration in Patients With Hypertension (ABC-H) Meta-Analysis

The prognostic importance of the nocturnal systolic blood pressure (SBP) fall, adjusted for average 24-hour SBP levels, is unclear. The Ambulatory Blood Pressure Collaboration in Patients With Hypertension (ABC-H) examined this issue in a meta-analysis of 17 312 hypertensives from 3 continents. Risks were computed for the systolic night-to-day ratio and for different dipping patterns (extreme, reduced, and reverse dippers) relative to normal dippers. ABC-H investigators provided multivariate adjusted hazard ratios (HRs), with and without adjustment for 24-hour SBP, for total cardiovascular events (CVEs), coronary events, strokes, cardiovascular mortality, and total mortality. Average 24-hour SBP varied from 131 to 140 mm Hg and systolic night-to-day ratio from 0.88 to 0.93. There were 1769 total CVEs, 916 coronary events, 698 strokes, 450 cardiovascular deaths, and 903 total deaths. After adjustment for 24-hour SBP, the systolic night-to-day ratio predicted all outcomes: from a 1-SD increase, summary HRs were 1.12 to 1.23. Reverse dipping also predicted all end points: HRs were 1.57 to 1.89. Reduced dippers, relative to normal dippers, had a significant 27% higher risk for total CVEs. Risks for extreme dippers were significantly influenced by antihypertensive treatment (P<0.001): untreated patients had increased risk of total CVEs (HR, 1.92), whereas treated patients had borderline lower risk (HR, 0.72) than normal dippers. For CVEs, heterogeneity was low for systolic night-to-day ratio and reverse/reduced dipping and moderate for extreme dippers. Quality of included studies was moderate to high, and publication bias was undetectable. In conclusion, in this largest meta-analysis of hypertensive patients, the nocturnal BP fall provided substantial prognostic information, independent of 24-hour SBP levels.

Towards a better understanding of QT interval variability

The International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) Guideline E14 recommends 'Thorough QT Study' as a standard assessment of drug-induced QT interval prolongation. At the same time, the value of drug-induced QTc prolongation as a surrogate marker for risk of life-threatening polymorphic ventricular tachycardia known as torsades des pointes remains controversial. Beat-to-beat variability of QT interval was recently proposed as an alternative metric. The following review addresses mechanisms of beat-to-beat QT variability, methods of QT interval variability measurements, and its prognostic value in clinical studies.

Evaluation of Tp-e interval and Tp-e/QT ratio in patients with non-dipper hypertension

AIMS

Non-dipper hypertension is associated with increased cardiovascular morbidity and mortality. Several studies have suggested that the interval from the peak to the end of the electrocardiographic T wave (Tp-e) may correspond to the transmural dispersion of repolarization and that increased Tp-e interval and Tp-e/QT ratio are associated with malignant ventricular arrhythmias. The aim of this study was to evaluate ventricular repolarization by using Tp-e interval and Tp-e/QT ratio in patients with non-dipper hypertension.

MATERIALS AND METHOD

This study included 80 hypertensive patients. Hypertensive patients were divided into two groups: 50 dipper patients (29 male, mean age 51.5 ± 8 years) and 30 non-dipper patients (17 male, mean age 50.6 ± 5.4 years). Tp-e interval and Tp-e/QT ratio were measured from the 12-lead electrocardiogram. These parameters were compared between groups.

RESULTS

No statistically significant difference was found between two groups in terms of basic characteristics. In electrocardiographic parameters analysis, QT dispersion (QTd) and corrected QTd were significantly increased in non-dipper patients compared to the dippers (39.4 ± 11.5 versus 27.3 ± 7.5 ms and 37.5 ± 9.5 versus 29.2 ± 6.5 ms, p = 0.001 and p = 0.01, respectively). Tp-e interval and Tp-e/QT ratio were also significantly higher in non-dipper patients (97.5 ± 11.2 versus 84.2 ± 8.3 ms and 0.23 ± 0.02 versus 0.17 ± 0.02, all p value <0.001).

CONCLUSION

Our study revealed that QTd, Tp-e interval and Tp-e/QT ratio are prolonged in patients with non-dipper hypertension.

Baroreceptor reflex dysfunction in the BACHD mouse model of Huntington's disease

Huntington’s disease is a progressive, neurodegenerative disorder that presents with a triad of clinical symptoms, which include movement abnormalities, emotional disturbance and cognitive impairment. Recent studies reported dysfunction of the autonomic nervous system in Huntington’s disease patients, which may contribute to the increased incidence of cardiovascular events in this patient population that often leads to death. We measured the baroreceptor reflex, a process dependent on proper autonomic function, in the BACHD mouse model of Huntington’s disease. We found a blunted response of the baroreceptor reflex as well as significantly higher daytime blood pressure in BACHD mice compared to WT controls, which are both indications of autonomic dysfunction. BACHD mice had increased heart weight to tibia length ratios at 7 and 12 mo of age suggesting hypertrophic changes of the heart, which we speculate is a response to the increased blood pressure and aberrant baroreceptor reflex. Despite these structural changes, the hearts of BACHD mice continue to function normally as assessed by echocardiographic analysis. Studies of autonomic and cardiovascular function in BACHD mice may help elucidate the pathophysiology of Huntington’s disease and aid in the development of clinical strategies to offset the incidence of fatal cardiovascular events in the Huntington’s disease patient population.