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Does shock index provide prognostic information in acute heart failure?
International Journal of Cardiology 215 (2016) 140–142
Contents lists available at ScienceDirect
International Journal of Cardiology journal homepage: www.elsevier.com/locate/ijcard
Correspondence
Does shock index provide prognostic information in acute heart failure? Leili Pourafkari, Christopher K. Wang, Michael Schwartz, Nader D. Nader ⁎ Dept. of Anesthesiology, 252 Farber Hall, Main Campus, State University of New York at Buffalo, Buffalo, NY 14214, United States
a r t i c l e
i n f o
Article history: Received 7 April 2016 Accepted 11 April 2016 Available online 14 April 2016 Keywords: Acute heart failure Shock Vital signs
To the editor: Acute heart failure (AHF) is currently regarded as an epidemic and is the leading cause of hospitalization in elderly [1]. Despite advances in the treatment, it remains a major cause of mortality and yet the assessment of its prognosis remains challenging. Shock index, defined as the ratio of heart rate (HR) to systolic blood pressure (SBP), was first proposed in 1967 as a simple and valuable tool for assessing volume status and an early indicator of shock in hemorrhagic and septic shock [2]. However as an easily calculated marker, its use expanded over years to various critical settings. Shock index has been shown to carry prognostic significance over conventional vital sign measurements in various critical settings including pulmonary embolism, myocardial infarction and even stroke [3–5]. Two adjustments for SI have been proposed which include diastolic blood pressure or age in the concept. Modified shock index (MSI), defined as the ratio of HR to mean arterial pressure (MAP) is developed to incorporate diastolic blood pressure in the assessment [6]. Age adjusted SI (AGESI) has recently been shown to be superior to SI/MSI in predicting mortality in an emergency department setting [7]. Admission SBP is recognized as an independent predictor of in-hospital and long-term mortality in AHF, and low SBP has been shown to correlate with worse outcomes [8,9]. The concept of SI has not yet been studied in the AHF population. We aimed to examine the sensitivity and specificity of SI, MSI and AGESI in predicting hospital and long-
⁎ Corresponding author. E-mail addresses: [email protected] (L. Pourafkari), [email protected] (C.K. Wang), [email protected] (M. Schwartz), [email protected] (N.D. Nader).
http://dx.doi.org/10.1016/j.ijcard.2016.04.083 0167-5273/Published by Elsevier Ireland Ltd.
term mortality in a population of patients with AHF. In a retrospective study, medical records of patients from the VA Western New York Healthcare System who were discharged with a primary diagnosis of AHF between January 2009 and January 2011, were examined. The study protocol indeed conformed to the ethical guidelines of Helsinki 1975 and was approved by local IRB. The study was exempted from informed consent for its retrospective nature. Collected data included all demographic and anthropometric characteristics, comorbid conditions and laboratory values. Data specific to the cardiovascular function consisted of those obtained from echocardiography and electrocardiography during each admission. Additionally, vital signs on presentation including mean arterial pressure, pulse pressure, HR, SI and MSI were recorded for each patient during each admission. All pertinent information was entered into a Microsoft Excel worksheet and then was transferred to SPSS version 22.0 (IBM®, Chicago, IL). SI and MSI were compared between the groups. The predictive value, sensitivity and specificity of SI and MSI were determined for predicting hospital mortality and were compared to those of AGESI among 554 admissions. Similarly, the predictive value, sensitivity and specificity of SI, MSI and AGESI were examined for predicting long-term mortality among 323 patients who survived the course of their first hospital admission. Mean age of patients was 77.1 ± 11.4 years. Thirty-one patients died during hospitalization. Men comprised 96.0% of 354 patients admitted with AHF. 87.7% had a history of hypertension, 76.8% were using beta-blockers on admission and 13.5% had permanent pacemakers. Median follow-up was 17.0 (0.5–82.9) months during which 188 additional patients died after discharge. Table 1 shows comparison of various vital sign measurements according to the hospital and long-term survival status. Though MAP and PP were significantly higher in patients who survived, HR, SI and MSI were not different among patients who survived the hospital course compared to those who died during hospitalization. Similar results were reported for long-term survival. However, AGESI on admission was significantly higher in patients who died either during hospitalization or in follow-up. Fig. 1 shows the ROC curve for hospital and long-term mortality prediction by AGESI. AGESI with a cut-off of 50.8 had a sensitivity of 46% and specificity of 71% for hospital morality. Additionally cut-off of 59.6 with a sensitivity of 54% and specificity of 83% could predict long-term mortality. Unlike other critical settings, SI and MSI on admission have failed to show any prognostic information in a population of patients admitted with AHF. It should be noted that AHF patients contrast other critical setting patients in some aspects. They are expectedly older, more frequently have hypertension and implanted
Correspondence
141
Table 1 Comparison of various vital sign measurements according to the survival status. Hospital mortality rates are calculated based on the number of the admissions while long-term mortality is presented on the unique number of the patients. P-values less than 0.05 are marked by asterisks.
Heart rate (bpm) Mean arterial pressure Pulse pressure Shock indexa Modified shock indexb a b
Hospital survivors (N = 523)
Deceased in hospital (N = 31)
P-value
Confidence interval (95%)
Long-term survivors (N = 135)
Long-term mortality (N = 188)
P-value
Confidence interval (95%)
80 ± 18 93 ± 16 59 ± 19 0.62 ± 0.18 0.89 ± 0.22
80 ± 23 85 ± 12 50 ± 20 0.66 ± 0.25 0.95 ± 0.26
0.056 0.012* 0.019* 0.480 0.136
−6.44, 7.02 1.62, 13.24 1.43, 13.24 −0.13, 0.06 −0.14, 0.02
84 ± 21 96 ± 15 62 ± 22 0.63 ± 0.20 0.88 ± 0.23
80 ± 16 91 ± 15 57 ± 19 0.64 ± 0.17 0.90 ± 0.21
0.089 0.002* 0.036* 0.826 0.524
−0.55, 7.75 1.96, 8.41 0.31, 9.11 −0.45, 0.03 −0.06, 0.31
Denotes “shock index”, calculated as the ratio of the heart rate over the systolic blood pressure at the time of admission. Denotes the “modified shock index”, calculated as the ratio of the heart rate over the mean arterial blood pressure measured at the time of admission.
pacemaker, and more frequently are taking beta-blocker medications. Normalized values for SI decline by increasing age [10]. All these factors contribute to the attenuated heart rate response observed in the state of hemodynamic stress in this population. Variation in predictive value of SI with age has been shown. These observations indicate that SI and MSI on admission in contrast to most critical settings may not be beneficial in predicting the hospital outcome in AHF. However, adjusting SI by age may increase its power to predict the hospital survival. Financial support No funding. Conflict of interest None was declared by any of the authors.
References [1] D. Farmakis, J. Parissis, J. Lekakis, G. Filippatos, Acute heart failure: epidemiology, risk factors, and prevention, Rev. Esp. Cardiol. (Engl. Ed.) 68 (2015) 245–248. [2] M. Allgower, C. Burri, “Shock index”, Dtsch. Med. Wochenschr. 92 (1967) 1947–1950. [3] S.J. McCall, S.D. Musgrave, J.F. Potter, R. Hale, A.B. Clark, M.A. Mamas, et al., The shock index predicts acute mortality outcomes in stroke, Int. J. Cardiol. 182 (2015) 523–527. [4] B. Huang, Y. Yang, J. Zhu, Y. Liang, H. Tan, L. Yu, et al., Usefulness of the admission shock index for predicting short-term outcomes in patients with ST-segment elevation myocardial infarction, Am. J. Cardiol. 114 (2014) 1315–1321. [5] A. Sam, D. Sanchez, V. Gomez, C. Wagner, D. Kopecna, C. Zamarro, et al., The shock index and the simplified PESI for identification of low-risk patients with acute pulmonary embolism, Eur. Respir. J. 37 (2011) 762–766. [6] Y.C. Liu, J.H. Liu, Z.A. Fang, G.L. Shan, J. Xu, Z.W. Qi, et al., Modified shock index and mortality rate of emergency patients, World J. Emerg. Med. 3 (2012) 114–117. [7] M. Torabi, A. Mirafzal, A. Rastegari, N. Sadeghkhani, Association of triage time Shock Index, Modified Shock Index, and Age Shock Index with mortality in Emergency Severity Index level 2 patients, Am. J. Emerg. Med. 34 (2016) 63–68.
Fig. 1. Receiver operating curve for hospital (left) and long-term mortality (right) prediction by SI, MSI and AGESI. AGESI: age-adjusted shock index, AUC: area under the curve, MSI: modified shock index, SE: standard error, SI: shock index.
142
Correspondence
[8] M. Gheorghiade, W.T. Abraham, N.M. Albert, B.H. Greenberg, C.M. O'Connor, L. She, et al., Systolic blood pressure at admission, clinical characteristics, and outcomes in patients hospitalized with acute heart failure, J. Am. Med. Assoc. 296 (2006) 2217–2226. [9] L. Pourafkari, S. Ghaffari, A.H. Afshar, S. Anwar, N.D. Nader, Predicting outcome in acute heart failure, does it matter? Acta Cardiol. 70 (2015) 653–663.
[10] L.D. Rappaport, S. Deakyne, J.A. Carcillo, K. McFann, M.R. Sills, Age- and sex-specific normal values for shock index in National Health and Nutrition Examination Survey 1999–2008 for ages 8 years and older, Am. J. Emerg. Med. 31 (2013) 838–842.
Contents lists available at ScienceDirect
International Journal of Cardiology journal homepage: www.elsevier.com/locate/ijcard
Correspondence
Does shock index provide prognostic information in acute heart failure? Leili Pourafkari, Christopher K. Wang, Michael Schwartz, Nader D. Nader ⁎ Dept. of Anesthesiology, 252 Farber Hall, Main Campus, State University of New York at Buffalo, Buffalo, NY 14214, United States
a r t i c l e
i n f o
Article history: Received 7 April 2016 Accepted 11 April 2016 Available online 14 April 2016 Keywords: Acute heart failure Shock Vital signs
To the editor: Acute heart failure (AHF) is currently regarded as an epidemic and is the leading cause of hospitalization in elderly [1]. Despite advances in the treatment, it remains a major cause of mortality and yet the assessment of its prognosis remains challenging. Shock index, defined as the ratio of heart rate (HR) to systolic blood pressure (SBP), was first proposed in 1967 as a simple and valuable tool for assessing volume status and an early indicator of shock in hemorrhagic and septic shock [2]. However as an easily calculated marker, its use expanded over years to various critical settings. Shock index has been shown to carry prognostic significance over conventional vital sign measurements in various critical settings including pulmonary embolism, myocardial infarction and even stroke [3–5]. Two adjustments for SI have been proposed which include diastolic blood pressure or age in the concept. Modified shock index (MSI), defined as the ratio of HR to mean arterial pressure (MAP) is developed to incorporate diastolic blood pressure in the assessment [6]. Age adjusted SI (AGESI) has recently been shown to be superior to SI/MSI in predicting mortality in an emergency department setting [7]. Admission SBP is recognized as an independent predictor of in-hospital and long-term mortality in AHF, and low SBP has been shown to correlate with worse outcomes [8,9]. The concept of SI has not yet been studied in the AHF population. We aimed to examine the sensitivity and specificity of SI, MSI and AGESI in predicting hospital and long-
⁎ Corresponding author. E-mail addresses: [email protected] (L. Pourafkari), [email protected] (C.K. Wang), [email protected] (M. Schwartz), [email protected] (N.D. Nader).
http://dx.doi.org/10.1016/j.ijcard.2016.04.083 0167-5273/Published by Elsevier Ireland Ltd.
term mortality in a population of patients with AHF. In a retrospective study, medical records of patients from the VA Western New York Healthcare System who were discharged with a primary diagnosis of AHF between January 2009 and January 2011, were examined. The study protocol indeed conformed to the ethical guidelines of Helsinki 1975 and was approved by local IRB. The study was exempted from informed consent for its retrospective nature. Collected data included all demographic and anthropometric characteristics, comorbid conditions and laboratory values. Data specific to the cardiovascular function consisted of those obtained from echocardiography and electrocardiography during each admission. Additionally, vital signs on presentation including mean arterial pressure, pulse pressure, HR, SI and MSI were recorded for each patient during each admission. All pertinent information was entered into a Microsoft Excel worksheet and then was transferred to SPSS version 22.0 (IBM®, Chicago, IL). SI and MSI were compared between the groups. The predictive value, sensitivity and specificity of SI and MSI were determined for predicting hospital mortality and were compared to those of AGESI among 554 admissions. Similarly, the predictive value, sensitivity and specificity of SI, MSI and AGESI were examined for predicting long-term mortality among 323 patients who survived the course of their first hospital admission. Mean age of patients was 77.1 ± 11.4 years. Thirty-one patients died during hospitalization. Men comprised 96.0% of 354 patients admitted with AHF. 87.7% had a history of hypertension, 76.8% were using beta-blockers on admission and 13.5% had permanent pacemakers. Median follow-up was 17.0 (0.5–82.9) months during which 188 additional patients died after discharge. Table 1 shows comparison of various vital sign measurements according to the hospital and long-term survival status. Though MAP and PP were significantly higher in patients who survived, HR, SI and MSI were not different among patients who survived the hospital course compared to those who died during hospitalization. Similar results were reported for long-term survival. However, AGESI on admission was significantly higher in patients who died either during hospitalization or in follow-up. Fig. 1 shows the ROC curve for hospital and long-term mortality prediction by AGESI. AGESI with a cut-off of 50.8 had a sensitivity of 46% and specificity of 71% for hospital morality. Additionally cut-off of 59.6 with a sensitivity of 54% and specificity of 83% could predict long-term mortality. Unlike other critical settings, SI and MSI on admission have failed to show any prognostic information in a population of patients admitted with AHF. It should be noted that AHF patients contrast other critical setting patients in some aspects. They are expectedly older, more frequently have hypertension and implanted
Correspondence
141
Table 1 Comparison of various vital sign measurements according to the survival status. Hospital mortality rates are calculated based on the number of the admissions while long-term mortality is presented on the unique number of the patients. P-values less than 0.05 are marked by asterisks.
Heart rate (bpm) Mean arterial pressure Pulse pressure Shock indexa Modified shock indexb a b
Hospital survivors (N = 523)
Deceased in hospital (N = 31)
P-value
Confidence interval (95%)
Long-term survivors (N = 135)
Long-term mortality (N = 188)
P-value
Confidence interval (95%)
80 ± 18 93 ± 16 59 ± 19 0.62 ± 0.18 0.89 ± 0.22
80 ± 23 85 ± 12 50 ± 20 0.66 ± 0.25 0.95 ± 0.26
0.056 0.012* 0.019* 0.480 0.136
−6.44, 7.02 1.62, 13.24 1.43, 13.24 −0.13, 0.06 −0.14, 0.02
84 ± 21 96 ± 15 62 ± 22 0.63 ± 0.20 0.88 ± 0.23
80 ± 16 91 ± 15 57 ± 19 0.64 ± 0.17 0.90 ± 0.21
0.089 0.002* 0.036* 0.826 0.524
−0.55, 7.75 1.96, 8.41 0.31, 9.11 −0.45, 0.03 −0.06, 0.31
Denotes “shock index”, calculated as the ratio of the heart rate over the systolic blood pressure at the time of admission. Denotes the “modified shock index”, calculated as the ratio of the heart rate over the mean arterial blood pressure measured at the time of admission.
pacemaker, and more frequently are taking beta-blocker medications. Normalized values for SI decline by increasing age [10]. All these factors contribute to the attenuated heart rate response observed in the state of hemodynamic stress in this population. Variation in predictive value of SI with age has been shown. These observations indicate that SI and MSI on admission in contrast to most critical settings may not be beneficial in predicting the hospital outcome in AHF. However, adjusting SI by age may increase its power to predict the hospital survival. Financial support No funding. Conflict of interest None was declared by any of the authors.
References [1] D. Farmakis, J. Parissis, J. Lekakis, G. Filippatos, Acute heart failure: epidemiology, risk factors, and prevention, Rev. Esp. Cardiol. (Engl. Ed.) 68 (2015) 245–248. [2] M. Allgower, C. Burri, “Shock index”, Dtsch. Med. Wochenschr. 92 (1967) 1947–1950. [3] S.J. McCall, S.D. Musgrave, J.F. Potter, R. Hale, A.B. Clark, M.A. Mamas, et al., The shock index predicts acute mortality outcomes in stroke, Int. J. Cardiol. 182 (2015) 523–527. [4] B. Huang, Y. Yang, J. Zhu, Y. Liang, H. Tan, L. Yu, et al., Usefulness of the admission shock index for predicting short-term outcomes in patients with ST-segment elevation myocardial infarction, Am. J. Cardiol. 114 (2014) 1315–1321. [5] A. Sam, D. Sanchez, V. Gomez, C. Wagner, D. Kopecna, C. Zamarro, et al., The shock index and the simplified PESI for identification of low-risk patients with acute pulmonary embolism, Eur. Respir. J. 37 (2011) 762–766. [6] Y.C. Liu, J.H. Liu, Z.A. Fang, G.L. Shan, J. Xu, Z.W. Qi, et al., Modified shock index and mortality rate of emergency patients, World J. Emerg. Med. 3 (2012) 114–117. [7] M. Torabi, A. Mirafzal, A. Rastegari, N. Sadeghkhani, Association of triage time Shock Index, Modified Shock Index, and Age Shock Index with mortality in Emergency Severity Index level 2 patients, Am. J. Emerg. Med. 34 (2016) 63–68.
Fig. 1. Receiver operating curve for hospital (left) and long-term mortality (right) prediction by SI, MSI and AGESI. AGESI: age-adjusted shock index, AUC: area under the curve, MSI: modified shock index, SE: standard error, SI: shock index.
142
Correspondence
[8] M. Gheorghiade, W.T. Abraham, N.M. Albert, B.H. Greenberg, C.M. O'Connor, L. She, et al., Systolic blood pressure at admission, clinical characteristics, and outcomes in patients hospitalized with acute heart failure, J. Am. Med. Assoc. 296 (2006) 2217–2226. [9] L. Pourafkari, S. Ghaffari, A.H. Afshar, S. Anwar, N.D. Nader, Predicting outcome in acute heart failure, does it matter? Acta Cardiol. 70 (2015) 653–663.
[10] L.D. Rappaport, S. Deakyne, J.A. Carcillo, K. McFann, M.R. Sills, Age- and sex-specific normal values for shock index in National Health and Nutrition Examination Survey 1999–2008 for ages 8 years and older, Am. J. Emerg. Med. 31 (2013) 838–842.