Managing the Complications of Mild Therapeutic Hypothermia in the Cardiac Arrest Patient.

Mild therapeutic hypothermia (MTH) is used to lower the core body temperature of cardiac arrest (CA) patients to 32°C from 34°C to provide improved survival and neurologic outcomes after resuscitation from in-hospital or out-of-hospital CA. Despite the improved benefits of MTH, there are potentially unforeseen complications associated during management. Although the adverse effects are transient, the clinician should be aware of the associated complications when managing the patient receiving MTH. We aim to provide the medical community comprehensive information related to the potential complications of survivors of CA receiving MTH, as it is imperative for the clinician to understand the physiologic changes that take place in the patient receiving MTH and how to prepare for them and manage them if they do occur. We hope to provide information of how to manage these potential complications through both a review of the current literature and a reflection of our own experience.

Relationship between quantitative cardiac neuronal imaging with ¹²³I-meta-iodobenzylguanidine and hospitalization in patients with heart failure.

PURPOSE: Hospitalization in patients with systolic heart failure is associated with morbidity, mortality, and cost. Myocardial sympathetic innervation, imaged by (123)I-meta-iodobenzylguanidine ((123)I-mIBG), has been associated with cardiac events in a recent multicenter study. The present analysis explored the relationship between (123)I-mIBG imaging findings and hospitalization. METHODS: Source documents from the ADMIRE-HF trial were reviewed to identify hospitalization events in patients with systolic heart failure following cardiac neuronal imaging using (123)I-mIBG. Time to hospitalization was analyzed with the Kaplan-Meier method and compared to the mIBG heart-to-mediastinum (H/M) ratio using multiple-failure Cox regression. RESULTS: During 1.4 years of median follow-up, 362 end-point hospitalizations occurred in 207 of 961 subjects, 79 % of whom had H/M ratio <1.6. Among subjects hospitalized for any cause, 88 % had H/M ratio <1.6 and subjects with H/M ratio <1.6 experienced hospitalization earlier than subjects with higher H/M ratios (log-rank p = 0.003). After adjusting for elevated brain natriuretic peptide (BNP) and time since heart failure diagnosis, a low mIBG H/M ratio was associated with cardiac-related hospitalization (HR 1.48, 95 % CI 1.05 - 2.0; p = 0.02). CONCLUSION: The mIBG H/M ratio may risk-stratify patients with heart failure for cardiac-related hospitalization, especially when used in conjunction with BNP. Further studies are warranted to examine these relationships.

Risk stratification of CAD with SPECT-MPI in women with known estrogen status.

OBJECTIVE: To compare exercise tolerance testing (ETT) with gated single photon emission computed tomography-myocardial perfusion imaging (SPECT-MPI) risk stratification in women with an intermediate to high CAD pretest risk and known estrogen status (ES). BACKGROUND: SPECT-MPI is an effective test for risk stratifying patients with stable angina. However in women, the current guidelines recommend the exercise tolerance testing (ETT) as first line test. Further, the relationship of stress imaging to ES, an independent risk indicator for CAD, is unknown. METHODS: 2,194 women with an intermediate to high CAD pre-test risk were referred for a clinically indicated ETT with gated SPECT-MPI. Duke treadmill scores (DTS) and summed stress score (SSS) were calculated. SSS were classified as normal (SSS < 3), mildly abnormal (SSS 4-8), or moderate-severely abnormal (SSS > 8). The ES was assessed as premenopausal, postmenopausal on hormone replacement therapy (HRT) as ES+ while postmenopausal not on HRT were ES-. An annualized cardiac event rate of a composite of cardiac death, unstable angina (UA) leading to hospitalization, non-fatal myocardial infarction, or late coronary revascularization was calculated for all the groups. RESULTS: The annualized cardiac event rate was 1.3% PPY, 2.1% PPY, and 3.2% PPY for low, intermediate, and high risk DTS (P = .2). Patients with intermediate DTS and mildly abnormal or moderate-severely abnormal gated SPECT-MPI had a significantly higher cardiac event rates (5.3% PPY and 10.8% PPY, respectively) than those with a normal gated SPECT-MPI (1.2%, PPY, P = .01). This was also demonstrated on further Cox-regression analysis. Risk stratification of SPECT-MPI over DTS was independent of ES. CONCLUSION: Gated SPECT-MPI provides risk stratification beyond standard exercise stress testing for women with suspected coronary artery disease, especially in patients with intermediate DTS and is independent of ES.

Major adverse cardiac events among postpercutaneous coronary intervention patients on clopidogrel and proton pump inhibitors.

OBJECTIVE: To determine if concomitant use of proton pump inhibitors (PPIs) and clopidogrel is associated with adverse events among postpercutaneous coronary intervention (PCI) patients. METHODS: This is a single-center, retrospective case-control study of 3,287 consecutive patients on clopidogrel who underwent PCI. Univariate and multivariate analyses determined if concomitant PPI and clopidogrel use was associated with major adverse cardiac events (MACE). RESULTS: There were significantly more deaths (3.0% vs 1.1%; P < 0.001), repeat revascularizations (3.8% vs 2.1%; P = 0.005) and MACE (7.1% vs 3.5%; P < 0.001) in the clopidogrel and PPI group. Cox regression revealed that PPI is an independent predictor of MACE (HR 1.70, 95% CI of 1.20-2.41; P = 0.003), mortality (HR 1.79; 95% CI 1.03-3.12, P = 0.038), and target-vessel revascularization (HR 1.75; 95% CI 1.12-2.72, P = 0.014). CONCLUSIONS: Concomitant use of PPIs and clopidogrel among post PCI patients was associated with increased rates of all-cause mortality, target vessel revascularization, and combined MACE at nine months follow-up.

Medical subspecialty hospitalist programs.

Hospital medicine is the fastest growing medical specialtyin the United States. Time pressures on primary-care physicians in the office and cost pressures on hospitals are the main driving forces behind this movement. Despite initial criticism and skepticism, hospitalist programs have proven cost effective in clinical and academic departments of internal medicine. These programs have recently been used in medical subspecialty departments as well. Hartford Hospital adopted a new specialty hospitalist program in its cardiovascular department. This program grew to become one of the most successful hospitalist programs in the hospital. Since better quality of care at a lower cost is the ultimate goal for any proposed health-care innovation, we predict that similar subspecialty hospitalist programs will become an accepted part of future hospital care. This article discusses specialty hospitalist care and describes our development of such a program at Hartford Hospital.

Use of prehospital electrocardiograms for the treatment of patients with ST-segment elevation myocardial infarction.

Use of prehospital electrocardiograms (ECG) by emergency medical personnel may reduce door-to-balloon (DTB) time in patients with ST-segment elevation myocardial infarction (STEMI) referred for urgent percutaneous coronary intervention (PCI). A 79-year-old female awoke from sleep with severe substernal chest pain and called 911 for assistance. The patient was initially evaluated by advanced life support paramedics who performed a 12-lead ECG at the patient's home. The ECG, which demonstrated an acute inferior STEMI, was transferred using a novel, web-based system to Hartford Hospital's Emergency Department. As a result of prehospital communication, the on-call catheterization team was mobilized prior to the patient's arrival. The patient underwent successful PCI of an occluded right coronary artery with a DTB time of 67 minutes and was subsequently discharged four days later. Use of prehospital electrocardiography combined with early catheterization laboratory mobilization allowed for timely STEMI reperfusion according to national guidelines, despite "off-hour" presentation.

Current Status of Patient Radiation Exposure of Cardiac Positron Emission Tomography and Single-Photon Emission Computed Tomographic Myocardial Perfusion Imaging.

BACKGROUND: Radiation exposure during nuclear cardiology procedures has received much attention and has prompted citations for radiation reduction. In 2010, the American Society of Nuclear Cardiology recommended reducing the average patient study radiation exposure to <9 mSv in 50% of studies by 2014. Cardiac positron emission tomography (PET) for myocardial perfusion imaging (MPI) has emerged within recent years, but current radiation exposure in cardiac nuclear PET laboratories is unknown. This study evaluated current reported patient radiation exposure from nuclear laboratories in the United States applying for Intersocietal Accreditation Commission accreditation for MPI using single photon emission computed tomography (SPECT) or PET. METHODS AND RESULTS: This was an analysis of nuclear cardiology studies submitted to the Intersocietal Accreditation Commission for either or both cardiac PET and SPECT accreditation. Cardiac SPECT data represented year 2015 while PET data combined years 2013 to 2015. Data was analyzed with χ2 and Mann-Whitney U tests (reported as median, 25th percentile, and 75th percentile). Reported PET MPI radiation exposure for 111 laboratories (532 patient cases) was 3.7 (3.2-4.1) mSv per study with no geographic variation. Reported SPECT MPI radiation exposure for 665 laboratories (3067 patient studies) was 12.8 (12.2-14.3) mSv. Highest radiation exposure was found in the South region. Technetium-only studies resulted in a median of 12.2 mSv per study. CONCLUSIONS: Radiation exposure from cardiac PET MPI in US laboratories applying for Intersocietal Accreditation Commission accreditation is low (111 laboratories, 3.7 mSv) and substantially lower than cardiac SPECT (665 laboratories, 12.8 mSv).

The Future of Cardiac Imaging: Report of a Think Tank Convened by the American College of Cardiology.

The American College of Cardiology's Executive Committee and Cardiovascular Imaging Section Leadership Council convened a discussion regarding the future of cardiac imaging among thought leaders in the field during a 2 day Think Tank. Participants were charged with thinking broadly about the future of imaging and developing a roadmap to address critical challenges. Key areas of discussion included: 1) how can cardiac imaging services thrive in our new world of value-based health care? 2) Who is the cardiac imager of the future and what is the role of the multimodality imager? 3) How can we nurture innovation and research in imaging? And 4) how can we maximize imaging information and optimize outcomes? This document describes the proceedings of this Think Tank.

Acid-base optimization during hypothermia.

Cardiac arrest (CA) often results in hemodynamic and metabolic compromise with associated poor prognosis. Therapeutic hypothermia (TH) has become the standard of care for CA survivors, decreasing reperfusion injury and intercellular acid-base disturbances, with improved neurologic outcomes. These benefits are realized despite a mild acidosis that can potentially occur during TH. By contrast, the severity of acidosis after return of spontaneous circulation (ROSC) must be monitored carefully and managed appropriately. Bicarbonate should be used only in case of severe acidosis and as a continuous infusion. The blood gas samples are usually warmed to 37 °C before analysis; hence, it is worth noting that the blood gas values are temperature dependent. Therefore, a calculated correction for values may be necessary.

The occurrence of shivering in cardiac arrest survivors undergoing therapeutic hypothermia is associated with a good neurologic outcome.

BACKGROUND: The incidence of shivering in cardiac arrest survivors who undergo therapeutic hypothermia (TH) is varied. Its occurrence is dependent on the integrity of multiple peripheral and central neurologic pathways. We hypothesized that cardiac arrest survivors who develop shivering while undergoing TH are more likely to have intact central neurologic pathways and thus have better neurologic outcome as compared to those who do not develop shivering during TH. METHODS: Prospectively collected data on consecutive adult patients admitted to a tertiary center from 1/1/2007 to 11/1/2010 that survived a cardiac arrest and underwent TH were retrospectively analyzed. Patients who developed shivering during the cooling phase of TH formed the "shivering" group and those that did not formed the "non-shivering" group. The primary end-point: Pittsburgh Cerebral Performance Category (CPC) scale; good (CPC 1-2) or poor (CPC 3-5) neurological outcome prior to discharge from hospital. RESULTS: Of the 129 cardiac arrest survivors who underwent TH, 34/94 (36%) patients in the "non-shivering" group as compared to 21/35 (60%) patients in the "shivering" group had good neurologic outcome (P=0.02). After adjusting for confounders using binary logistic regression, occurrence of shivering (OR: 2.71, 95% CI 1.099-7.41, P=0.04), time to return of spontaneous circulation (OR: 0.96, 95% CI 0.93-0.98, P=0.004) and initial presenting rhythm (OR: 4.0, 95% CI 1.63-10.0, P=0.002) were independent predictors of neurologic outcome. CONCLUSION: The occurrence of shivering in cardiac arrest survivors who undergo TH is associated with an increased likelihood of good neurologic outcome as compared to its absence.

The impact of severe acidemia on neurologic outcome of cardiac arrest survivors undergoing therapeutic hypothermia.

INTRODUCTION: Therapeutic Hypothermia (TH) has become a standard of care in improving neurological outcomes in cardiac arrest (CA) survivors. Previous studies have defined severe acidemia as plasma pH<7.20. We investigated the influence of severe acidemia at the time of initiation of TH on neurological outcome in CA survivors. METHODS: A retrospective analysis was performed on 196 consecutive CA survivors (out-of-hospital CA and in-hospital CA) who underwent TH with endovascular cooling between January 2007 and October 2012. Arterial blood gas drawn prior to initiation of TH was utilized to measure pH in all patients. Shockable and non-shockable CA patients were divided into two sub-groups based on pH (pH<7.2 and pH≥7.2). The primary end-point was measured using the Pittsburgh Cerebral Performance Category (CPC) scale prior to discharge from the hospital: good (CPC 1 and 2) and poor (CPC 3 to 5) neurologic outcome. RESULTS: Sixty-two percent of shockable CA patients with pH≥7.20 had good neurological outcome as compared to 34% patients with pH<7.20. Shockable CA patients with pH≥7.20 were 3.3 times more likely to have better neurological outcome when compared to those with pH <7.20 [p=0.013, OR 3.3, 95% CI (1.28-8.45)]. In comparison, non-shockable CA patients with p≥7.20 did not have a significantly different neurological outcome as compared to those with pH<7.20 [p=0.97, OR 1.02, 95% CI (0.31-3.3)]. CONCLUSION: Presence of severe acidemia at initiation of TH in shockable CA survivors is significantly associated with poor neurological outcomes. This effect was not observed in the non-shockable CA survivors.

Therapeutic hypothermia is associated with improved neurologic outcome and survival in cardiac arrest survivors of non-shockable rhythms.

BACKGROUND: Therapeutic hypothermia improves neurologic outcomes in patients resuscitated from cardiac arrest due to ventricular fibrillation. However, its role in patients with cardiac arrest due to non-shockable rhythms (pulseless electrical activity (PEA) and asystole) is unclear. We hypothesized that therapeutic hypothermia favorably impacts neurologic outcome and survival in patients resuscitated from cardiac arrest due to non-shockable rhythms. METHODS: Retrospectively collected data on consecutive adult patients admitted to Hartford Hospital from 1/1/2004 to 11/1/2010 who survived a cardiac arrest due to PEA or asystole were analyzed. Patients who underwent therapeutic hypothermia (1/1/2007-11/1/2010) formed the hypothermia group while patients admitted prior to the institution of therapeutic hypothermia (1/1/2004-1/1/2007) at Hartford Hospital formed the control group. The primary end-point was measured using the Pittsburgh cerebral performance category (CPC) scale and patients were assessed for a good (CPC 1 and 2) or poor (CPC 3-5) neurological outcome prior to discharge from hospital. A secondary end-point was measured as survival at discharge from hospital. RESULTS: Of 100 post-cardiac arrest patients included in the study, 15/52 (29%) patients in the hypothermia group had a good neurologic outcome as compared to 5/43 (10%) patients in the control group (P=0.021). On multivariate analysis, the odds ratio for good neurologic outcome and survival at discharge from the hospital with therapeutic hypothermia as compared to control were 4.35 (95% CI 1.10-17.24, P=0.04) and 5.65 (CI 1.66-19.23, P=0.006) respectively. CONCLUSION: Therapeutic hypothermia is associated with favorable neurologic outcome and survival in patients resuscitated after cardiac arrest due to non-shockable rhythms.

The use of hypothermia therapy in cardiac arrest survivors.

The annual incidence of out-of-hospital cardiac arrests in the United States is ∼350,000-450,000 per year. The prognosis for cardiac arrest survivors remains extremely poor. Therapeutic hypothermia (TH) is the only therapy proven to improve survival and neurological outcome in these patients. This article discusses the pathophysiology of neurological injury in cardiac arrest survivors and states the presumed mechanisms by which TH mitigates brain injury in these patients. It reviews the contraindications to the use of this therapy, methods of cooling, and phases of TH and elaborates on the intensive care unit management of TH. The use of TH in ventricular fibrillation survivors has become the standard of care and continues to evolve in its application as an essential therapy in cardiac arrest patients.