Clinical Research in Cardiology

, Volume 102, Issue 8, pp 593–598

Heart rate differentiates urgency and emergency in hypertensive crisis

Authors

    • Cardiology Unit, Internal Medicine DepartmentSalmaniya Medical Complex
    • Department of Internal MedicineArabian Gulf University
  • Michael Böhm
    • Klinik für Innere Medizin III, Universitätsklinikum des Saarlandes
  • Aysha Husain
    • Cardiology Unit, Internal Medicine DepartmentSalmaniya Medical Complex
Original Paper

DOI: 10.1007/s00392-013-0570-5

Cite this article as:
Al Bannay, R., Böhm, M. & Husain, A. Clin Res Cardiol (2013) 102: 593. doi:10.1007/s00392-013-0570-5

Abstract

Objective

To study the clinical significance of presenting blood pressure parameters and heart rate in patients with hypertensive crisis.

Methods

In patients admitted with hypertensive crisis between January 2011 and May 2011, demography, mode of presentation, co-morbidities, blood pressure readings, and heart rate at presentation were documented. Further clustering of hypertensive crisis into emergency or urgency was based on the presence or absence of target organ involvement. The relationship between blood pressure parameters, heart rate, and other variables was analyzed.

Results

189 patients in sinus rhythm were enrolled in this pilot study. The rate of hypertensive urgency was 56 %, whereas the rate of hypertensive emergency was 44 %, respectively. Subjects with hypertensive emergency had a higher mean heart rate (93 ± 22.7 bpm) than those with urgency (81 ± 11.5 bpm) (P = 0.015). Women had higher heart rates (92 ± 18.5 bpm) than men (86 ± 17.6 bpm) (P = 0.014). Heart rates below 100 bpm had a specificity of 94 %, classifying patients as hypertensive urgency. Tachycardia had a powerful statistical association with hypertensive left ventricular failure (P < 0.0001). Other hemodynamic parameters, including systolic blood pressure, diastolic blood pressure, pulse pressure, and mean blood pressure relates neither to urgency nor to emergency. Diabetic patients with HBA1c levels of more than 53 mmol/mol had a heart rate of more than 100 bpm (P = 0.015) during hypertensive crisis.

Conclusions

Normal heart rate is characteristic of hypertensive urgency. Tachycardia in this setting is an ominous sign and denotes hypertensive complications in particular left ventricular failure. Among diabetics, elevated heart rate is associated with poor glycemic control.

Keywords

Hypertensive crisisHeart rateTachycardiaHypertensive emergencyHypertensive urgencyLeft ventricular failureGlycated hemoglobin

Introduction

The role of heart rate in predicting cardiovascular events has captured the attention of clinical investigators. The concept of the cardiovascular continuum by Dzau and Braunwald [1] incorporated the role of various risk factors in the pathogenesis of cardio-cerebrovascular pathologies with their clinical sequences. Accumulated clinical and experimental evidences imply that heart rate can be integrated into the chain of pathophysiological mechanisms in the cardiovascular continuum [25]. The direct relationship between elevated heart rate and cardiovascular morbidity and mortality is well established [611].

In hypertension, with increasing heart rate (>80 to <120 bpm), the proportion of patients with microalbuminuria increased from 63 to 69 % [12]. Microalbuminuria is a known marker of cardiovascular outcomes [13].

The definition of hypertensive crisis relies on absolute blood pressure and such numerical digits cannot verify the hypertensive crisis being urgent or emergent. Other clinical tools might be important to differentiate the two conditions.

In this observational cross-sectional study, we aim to investigate the role of blood pressure parameters and heart rate in patients with hypertensive crisis. Isolated systolic hypertension, diabetes mellitus, and poor adherence to treatments are validated predictors for hypertensive crises [1418]. Furthermore, presenting clinical signs and symptoms can also differentiate hypertensive emergency versus urgency. Shortness of breath and neurologic deficits indicate hypertensive emergency, whereas giddiness and headache are typical for hypertensive urgency [16]. Heart rate in hypertensive crisis is an easily obtainable clinical sign. Its utility for risk categorization in the emergency room for these patients has yet to be defined. This study is the first of its kind to inspect its role in this acute setting.

Methodology

Included patients are those aged above 18 years, admitted with hypertensive crisis and were in sinus rhythm. The study period was January 2011 to May 2011. The demographic parameters, mode of presentation, co-morbidities, systolic blood pressure, diastolic blood pressure, pulse pressure, mean blood pressure and heart rate at presentation were documented. Tachycardia is defined as a heart rate ≥100 bpm [19]. Preexisting medications and the adherence of patients to them were verified at the time of recruitment.

The state of hypertensive crisis is defined as a systolic blood pressure of ≥180 mmHg or diastolic blood pressure of ≥120 mmHg. This is the definition adopted by the JNC VII and the update of the European Society of Hypertension Guidelines [20, 21]. Further clustering of hypertensive crises into emergency or urgency is based on the presence or absence of target organ involvement. Acute target organ involvement, such as acute coronary syndrome or acute left ventricular failure (LVF) will sub-classify these patients into hypertensive emergency. Their absence will define hypertensive urgency [20, 21]. The study was conducted at the cardiology unit of the Salmaniya Medical Complex, Manama, Kingdom of Bahrain. Salmaniya Medical Complex, a university-affiliated hospital, is a referral center for secondary and tertiary treatment, providing 24-h medical care for approximately 1.2 million inhabitants, who have free access to medical care through direct contact or referral from other medical services (governmental and private).

Blood pressure was measured using a Vital Signs 300 monitor (Welch Allyn, Inc., Skaneateles Falls, NY, USA) on two separate occasions (5 min apart). The patient was introduced into the analysis if both readings satisfied the definition of hypertensive crisis mentioned above. This device has been validated for automated blood pressure monitoring [22]. Hypertensive emergency was differentiated from hypertensive urgency based on the clinical history, physical examination, and relevant diagnostic tests (blood test, chest X-ray, electrocardiogram (ECG) and CT scan). Heart rate was calculated from the ECG in the emergency room performed within 15 min since patient’s arrival. Patients were considered to have diabetes mellitus, if two readings of fasting blood glucose, taken on separate occasions, exceeded 7 mmol/L, if symptoms of diabetes occurred with a casual plasma glucose concentration ≥200 mg/dl (11.1 mmol/L), or if the 2-h post-load glucose level was ≥200 mg/dl (11.1 mmol/L) during an oral glucose tolerance test (OGTT) [23]. Dyslipidemia (hypercholesterolemia) was diagnosed, if the total cholesterol level exceeded 200 mg/dl (5.2 mmol/L) [24]. Furthermore, renal impairment was diagnosed when the estimated glomerular filtration rate (GFR) was < 90 ml/min/1.73 m2 [25].

Patients younger than 18 years old or with uncontrolled hypertension were excluded from the study, if their blood pressure level did not match the definition of the Joint National Committee or the European Society of Hypertension for a hypertensive crisis. Furthermore, as tachycardia in atrial fibrillation does not always have the same clinical significance or mechanism as in sinus tachycardia, patients with non-sinus rhythm were excluded.

Statistical analysis

Statistical analysis was performed for 189 subjects, who met the inclusion criteria. A descriptive analysis of the qualitative variables and the results were conducted using the Statistical Package for the Social Sciences (SPSS) software, Version 21 (SPSS-IBM, Chicago, IL, USA). Comparisons of patients’ characteristics between hypertensive emergency and hypertensive urgency were performed using the Chi-square test, Fisher’s exact, and Cramer’s V test. The mean of the studied hemodynamic variables was correlated with types of hypertensive crisis utilizing the ANOVA method. This was followed by an appropriate post hoc test in the case significant difference was present. The P value of 0.05 or less was taken as a criterion for a statistically significant difference.

Results

The data from 189 patients, who met the inclusion criteria were prospectively collected during the study period. Male gender dominated the study subjects, while females were older (61 vs. 52 years) (Table 1). Women had higher mean heart rate (92 ± 18.5 bpm) than men (86 ± 17.6 bpm) (P = 0.014).
Table 1

Characteristics of studied patients

Variable

N (%)

Total subjects

189

Male

119 (63)

Female

70 (37)

HTN urgency

106 (56)

HTN emergency

83 (44)

LVF

36 (43)

ACS

32 (38)

Stroke

15 (18)

Diabetes mellitus

87 (46)

HTN Hypertension; LVF left ventricular failure; ACS acute coronary syndrome

The rate of urgency was 56 %, while the rate of emergency was 44 % (Table 1). Out of the urgency group who were 106, 100 patients had a heart rate of less than 100 (94 %). The emergency group had a significantly higher mean heart rate than the urgency counterpart (P = 0.0001) (Table 2). Collectively, the mean heart rate of the emergency group was less than 100 (93 ± 22.7 bpm). Although distinctly hypertensive LVF subjects had a mean heart rate of (106 ± 21 bpm) (P < 0.0001). (Table 3) Palpitation and shortness of breath as symptoms had a close relation with tachycardia as a sign (Table 4). Yet, within the emergency group, patients with stroke and ACS had mean heart rates below 100 (86 ± 21.5 and 84 ± 20 bpm, respectively) (Table 3). The analysis of blood pressure parameters did not show significant associations with various hypertensive emergencies (Table 3). Of the patients in the urgency group, 96 (90 %) were previously known to have hypertension. Among them, 13 (12 %) were prescribed beta blockers. Contrarily, all patients, who presented with hypertensive emergency known to suffer from hypertension beforehand. In addition, 54 (65 %) of them were on prior beta blocker therapy. Poor compliance was confirmed in 22 % of total subjects. The majority of the hypertensive emergencies were among diabetics (71 %).
Table 2

Hemodynamic parameters among patients with hypertensive crisis

Hemodynamic variable

HTN urgency

HTN emergency

P value

Heart rate

81 (±11.5)

93 (±22.7)

0.0001

Systolic Bp

203 (±22.5)

195 (±18.4)

NS

Diastolic Bp

113 (±18.6)

110 (±15.8)

NS

Mean Bp

143 (±16.4)

138 (±13.4)

NS

Pulse pressure

89 (±25.3)

85 (±22.7)

NS

HTN hypertension; Bp blood pressure; NS non significant

Data expressed as mean (±SD)

Table 3

Hemodynamic variables among different types of hypertensive emergency groups

Hemodynamic variable

Types of hypertensive emergency crisis

P value

LVF (N = 36)

ACS (N = 32)

Stroke (N = 15)

Heart rate

106 (±21)

86 (±21.5)

84 (±20)

0.0001

Systolic Bp

202 (±20.8)

197 (±17.2)

199 (±10)

NS

Diastolic Bp

113 (±17.2)

108 (±13.2)

107 (±17.4)

NS

Mean Bp

141 (±14.6)

137 (±11.9)

137 (±12.6)

NS

Pulse pressure

88 (±27.1)

89 (±20.7)

92 (±15.3)

NS

LVF left ventricular failure; ACS acute coronary syndrome; Bp blood pressure; NS non significant

Data expressed as mean (±SD)

Table 4

Frequency of signs and symptoms between two groups

Signs and symptoms

Heart rate <100/min

N (%)

Heart rate >100/min

N (%)

P value

Headache

54 (37)

11 (20)

NS

Shortness of breath (SOB)

32 (22)

27 (49)

0.0001

Limb weakness

19 (13)

3 (5)

NS

Chest pain

48 (32)

22 (40)

NS

Palpitation

12 (8)

16 (29)

0.009

Dizziness

29 (20)

5 (9)

NS

NS non significant

Moreover, diabetic subjects with glycated hemoglobin of more than 53 mmol/mol had a tendency to have higher heart rates during hypertensive crisis (P = 0.015) (Fig. 1).
https://static-content.springer.com/image/art%3A10.1007%2Fs00392-013-0570-5/MediaObjects/392_2013_570_Fig1_HTML.gif
Fig. 1

Heart rate among diabetic patients with HBA1c below and above 53 mmol/mol (P < 0.015)

Discussion

Because the clinical role of heart rate during hypertensive crisis has not been previously studied, this investigation is the first that highlights such an association. As our data suggested, the presenting heart rate during hypertensive crisis provides significant prediction to clinical complications. Heart rate below 100 is highly specific for predicting hypertensive urgency (specificity of 94 %). The mean heart rate during hypertensive emergency was significantly higher than during urgency. One sub-analysis of the LIFE trial has shown that an increment of 10 beats above 84 bpm is associated with 44 % increase in cardiovascular death [26]. In contrast to our study, the above cohort analyzed the resting heart rate among patients with hypertension remote of hypertensive crisis episodes [26]. Multiple heart rate readings were evaluated rather than a single occasion record. Yet, the presenting heart rate during various medical emergencies should not be underestimated [27]. It is commenced as one component of outcome scores in intensive care medicine and in patients with multiple organ dysfunctions [28, 29]. Custodis et al. [5] demonstrated that subjecting rats to acute stress could provoke abrupt increase in heart rate, but no difference in the mean arterial blood pressure [5]. These findings were substantiated recently in patients with sustained non-hemorrhagic injury. The rise in heart rate outweighed the elevation in systolic blood pressure in this acute setting [30]. In this study, unlike the heart rate, blood pressure parameters failed to show such significant association with the hypertensive emergency or urgency. Blood pressure levels help to define hypertensive crisis state, but cannot differentiate urgency from emergency. Incorporating heart rate as a clinical sign can segregate hypertensive emergency from urgency appears persuasive and sets the stage for future studies.

Patients with hypertensive emergency had elevated heart rate compared to individuals with hypertensive urgency. The elevation in heart rate was marked in LVF patients (106 bpm), marginal in ACS (86 bpm) and least in stroke (84 bpm). Overall, a heart rate of more than 100 had a positive predictive value of 86 % for detecting hypertensive emergencies. Recently, Ritter et al. [31] studied heart rate effects in acute stroke. They demonstrated that heart rate was variable during acute stroke. Elevated heart rate usually denotes cardiac emboli in the setting of atrial fibrillation. The mean heart rate on admission was 78 bpm [31]. Analyzing the mean heart rate in ACS regional and international registries revealed that the mean heart rate ranges from 79 to 84 bpm, which is coinciding with our observation in hypertensive crisis [32, 33].

Tachycardia had a powerful statistical association with hypertensive LVF (P < 0.0001). Such association was not related to ejection fraction. The deleterious effect of tachycardia on failing hearts being systolic or diastolic is well known. The mechanisms linking heart rate and heart failure are unclear [34]. Tachycardia is known to compromise the diastolic fillings that will ultimately cause reduction in stroke volume. Reil et al. [35] demonstrated the link between tachycardia and decreased stroke volume and enhanced stroke work even in preserved systolic function. Further reduction in stroke volume might be anticipated among patients with heart failure (Fig. 2) [35]. In this setting in addition of being a marker for complication, tachycardia could be a therapeutic target. Reducing elevated capillary pulmonary wedge pressure by heart rate reduction as tested in heart failure with elevated heart rate [35, 36] could be an option in complicated hypertensive crisis with congestion. However, the worth of this approach will have to be scrutinized in future studies.
https://static-content.springer.com/image/art%3A10.1007%2Fs00392-013-0570-5/MediaObjects/392_2013_570_Fig2_HTML.gif
Fig. 2

Pressure–volume analysis of left ventricular stroke volume (SV) and stroke work (shaded area) via arterial elastance relations (Ea and Ea′). The shaded area between both curves represents the whole stroke work, a measure of the corresponding myocardial oxygen consumption (MVO2) per heart beat. Ordinate: pressure in mmHg; coordinate: volume in milliliters. a Typical PV analysis in a healthy patient. b Typical PV analysis in patients with systolic heart failure (flattened ESPVR) and increased Ea′. EDPVR end-diastolic pressure–volume relation; ESPVR end-systolic pressure–volume relation; SV′ reduced stroke volume with increased stroke work after increase of Ea to Ea′ induced by increase in TPR, HR, or both. After reference [35] © 2009, Elsevier BV

High heart rates have been shown to be targets for intervention and prognostication of outcomes in chronic heart failure with left ventricular systolic dysfunction [11]. In SHIFT, ivabradine has been shown to decrease the composite endpoint of cardiovascular mortality and heart failure hospitalizations in patients with systolic heart failure [11]. Ivabradine is a unique pharmacotherapeutic agent that has pure heart rate-lowering effect without any other hemodynamic interference. Accordingly, its favorable response is entirely exerted by only heart rate reduction [11]. Despite being on beta blockers (28 out of 36 patients with heart failure (70 %), some of our patients were tachycardic. Similar observations were noted by the Euro Heart Survey, in which some patients on beta blockers did not have their tachycardia blunted during acute pulmonary edema [37]. We found that diabetics with poor glycemic control (HbA1c >53 mmol/mol) were more tachycardiac during hypertensive crisis. Elevated basal heart rate with reduced heart variability among diabetics is well known and can be attributed to autonomic neuropathy [38]. Moreover, poorly uncontrolled diabetes is a risk factor for hypertensive emergency; hence tachycardia and diabetes may act in concert to promote this condition [17].

Study limitations

There are some limitations that have to be addressed. A study on emergency conditions in a single center can only employ a relatively small sample size.

However, this is to the best of our knowledge, the largest and first single center cohort on hypertensive emergencies evaluating heart rate. A heart rate cutoff point of 100 bpm, which is the current threshold to define tachycardia, as a cardiovascular risk discriminator is high. The data of the literature are sound and indicate that this digit should be set to probably around 85 bpm [39]. Cardiovascular morbidities and mortalities are related to even lower heart rates [26]. This pilot study did not investigate the prognostic significance of the presenting heart rate on major adverse cardiac outcomes upon follow-up, but set the stage for future studies where more patients will be recruited with extended follow-up to judge long-term outcomes.

Conclusions

Normal heart rate during hypertensive crisis is related to hypertensive urgency. Elevated presenting heart rate during hypertensive emergency is more than hypertensive urgency, despite similar levels of blood pressure parameters. Tachycardia accompanied by shortness of breath is an ominous sign during hypertensive crisis and can indicate or even promote acute LVF. Poorly controlled diabetics had a tendency to have a higher heart rate during hypertensive crisis. Future studies should address the potential value of heart rate-lowering medications in hypertensive crisis.

Conflict of interest

The authors of this manuscript declare no conflict of interests.

Copyright information

© Springer-Verlag Berlin Heidelberg 2013