Zohaib Akhter  ( Tabba Heart Institute, Karachi, Pakistan )
Sajid Hussain  ( Tabba Heart Institute, Karachi, Pakistan )
Saba Aijaz  ( Tabba Heart Institute, Karachi, Pakistan )
Saadia Sattar  ( Tabba Heart Institute, Karachi, Pakistan )
Asad Pathan  ( Tabba Heart Institute, Karachi, Pakistan )

Objective: To assess the frequency of acute coronary syndrome patients with cardiogenic shock and not undergoing revascularisation, their in- hospital outcome and reasons underlying management decisions.

Methods: The retrospective cross-sectional study was conducted at Tabba Heart Institute, Karachi, and comprised data from July 2013 to December 2017 of acute coronary syndrome with hypotension and not having under gone revascularisation. Data was analyzed using Stata 12.1.
Results: Of the 383 patients, 55(14.3%) did not undergo revascularisation. Overall mean age was

63.2±9.8years. Overall mortality was 45(81.8%). Revascularisation was intended in 28(51%) patients of whom 19(68%) died before undergoing cardiac catheterisation. Another 9(32%) patients died after cardiac catheterisation but before revascularisation. Common clinical reasons in the remaining 27(49%) patients not considered for revascularisation were hypoxic brain injury secondary to cardiac arrest, patient refusal, perceived patient frailty, multi-organ failure, sepsis or pre-existing stroke/ malignancy.

Conclusion: Cardiogenic shock complicating myocardial infarction not treated by revascularization had a very poor early outcome. In the two-third of patients before treatment was initiated, there was cardiac arrest with failed resuscitation or poor recovery.

Keywords: Shock, Cardiogenic, Acute coronary syndrome, Non-revascularised. (JPMA 69: 1663; 2019). doi: 10.5455/JPMA.20977.

Introduction

Cardiogenic shock (CS) develops in 5-15% of patients presenting with acute myocardial infarction (MI).¹ CS is defined as systolic blood pressure (SBP) of less than 90 mmHg and/or use of vasopressor agents to stabilise the blood pressure (BP) in the absence of volume depletion. It occurs as a result of end-organ hypo-perfusion state due to reduced cardiac output, typically from extensive left ventricular dysfunction (LVD) and is associated with decrease in urine output, altered conscious status and cold extremities, depending upon the severity of haemodynamic compromise. Management of CS includes early revascularisation, mechanical circulatory support and aggressive pharmacological management. ² Early revascularization in CS has shown improved long-term prognosis in randomised clinical trials (RCTs) and studies published from large registries.5,6 Despite changes in therapeutic approach, mortality in CS patients continues to remain high at 40-50%.^3,4 Although all consensus guidelines recommend early revascularisation in CS patients, 30-50% of such patients from western registries do not undergo early revascularisation.^5-7 There are no local or regional registries; and even North American or European registries reporting CS do not document reasons for not administering revascularisation in these patients. Similarly, there is a paucity of data from South Asia, including Pakistan, on CS patients managed without revascularisation. Recognising such patients early in their care journey may allow initiation of more advanced therapies that may alter the outcome in these very high-risk patients. The current study was planned to assess the frequency of these patients, their in-hospital outcome and the reasons underlying these management decisions.

Methods

The retrospective cross-sectional study was conducted at Tabba Heart Institute Karachi, which is a single-specialty, heart-only, tertiary care hospital. Data was obtained from the catheterisation laboratory and acute coronary syndrome (ACS) database maintained according to the standard National Cardiovascular Data Registry (NCDR) and Acute Coronary Treatment and Intervention Outcomes Network (ACTION) registry definitions.^8,9 The study questionnaire was designed in line with the registry questions that included data on all CS patients admitted with ACS, their characteristics, clinical presentation such as Killip class (to quantify severity of myocardial infarction in ACS and predict risk of 30-day mortality), treatments, and outcomes. CS was defined by the presence of hypotension i.e. SBP <90mmHg for at least 30 minutes and/or need for one or more vasopressor agents to maintain SBP >90 mm/Hg in the absence of hypovolemia along with clinical presentation of ACS. Data of ACS patients with ST-elevation MI (STEMI) or Non-STEMI, who developed CS at the time of arrival in emergency room (ER) or during hospital stay, was included. Data of patients with shock in the absence of significant coronary artery disease (CAD) or shock due to acute MI rupture complications was excluded. Non-purposive consecutive sampling technique was used. Approval was obtained from institutional ethics review committee. Data was analysed using Stata 12.1. Normality of the continuous variables was assessed using Shapiro-Wilk test. Means and standard deviation (SD) were calculated for quantitative variables, such as age, initial haemoglobin (Hb), glomerular filtration rate (GFR), arrival heart rate (HR) and systolic blood pressure (SBP) at arrival. Frequency and percentages were calculated for categorical variables. Fischer's exact test was used for categorical variables, and independent sample t-test or Mann-Whitney U test was used for quantitative variables depending upon normality of independent variables to assess relationship with discharge status.

Results

Of the383 patients hospitalized during the study period, 55(14.3%) met the inclusion criteria. Of them, 44(80%) were males and 11(20%) were females. Overall mean age was 63.2±9.8 years and 6(10.9%) patients were >75 years. Median time from symptom onset to hospital arrival was 9.5hours (inter-quartile range [IQR]: 43.6 hours). Diabetes was present in 28(50.9%) and hypertension in 34(61.8%) patients. Clinical presentation was STEMI in 34(61.8%) patients. Pre-existing CAD was present in 14(25.5%) patients. While in hospital, 33(60.0%) patients had a cardiac arrest (Table).



Overall mortality was 45(81.8%). Revascularisation was intended in 28(51%) patients of whom 19(68%) died before undergoing cardiac catheterisation (median time from admission: 2.8hours, IQR: 5.7 hours). Another 9(32%) patients died after cardiac catheterisation but before revascularisation could be performed. These 9(32%) patients had severe left main and multi-vessel disease (median time from admission: 2.4hours, IQR: 3.3hours).The deceased patients had a higher proportion of 2 vasopressor use 16(35.5%) and cardiac arrest 31(68.9%) at presentation. Common clinical reasons in the remaining 27(49%) patients for not considering revascularization were hypoxic brain injury secondary to cardiac arrest, patient refusal, multi-organ failure, sepsis, cerebro-vascular accident (CVA) or pre-existing malignancy (Figure).



Median length of hospital stay was 3 days (IQR: 5).

Discussion

The study assessed the clinical characteristics, in-hospital management, decision-making and outcome of 55 patients who presented with ACS complicated by CS who did not undergo revascularisation. It was observed that these patients had exceptionally high mortality and usually presented with long ischaemic time, STEMI in majority and a high frequency of cardiac arrest early in the hospital course. In over two-third of these patients , revascularisation was considered but the patients had early cardiac arrest and failed resuscitation or extensive hypoxic brain injury before revascularisation could be performed. In the remaining patients, revascularization was not performed due to non-cardiac systemic conditions or patient preference. Patients with ACS and CS who did not undergo revascularisation comprised 14.3% of the overall ACS-CS group. This is much smaller than the 30-50% reported from United States or European registries of ACS or STEMI. ¹⁰ As the reasons for not proceeding with revascularisation in the Western registries are not described, it is difficult to make a comparison. Since this is a single-centre cardiac-only registry, it is likely that there is a selection bias in the patients getting referred here. Patients with CS being admitted to general hospitals who were not considered candidates for revascularization by their treating physicians were probably not referred to our institution. The overall mortality in the study was over 80%, although half of the patients were intended for revascularization and died before it could be carried out. Excluding these, the mortality in the remaining patients was around 60%. This is comparable to the 60-70% in the medically treated patients in the randomised Should We Emergently Revascularise Occluded Coronaries (SHOCK) trial and earlier registries where patients where medically managed with or without use of intra-aortic balloon pump(IABP). ¹¹ The most common reason in our study for patients not getting revascularisation was cardiac arrest and unsuccessful resuscitation or extensive brain injury either prior to cardiac catheterisation or before carrying out revascularisation. These patients are in general critically ill and allow a very limited window of treatment. In patients with refractory cardiac arrest, early use of Veno-Arterial Extra -Corporeal Membrane Oxygenation (VA-ECMO) may facilitate a bridging opportunity for other therapies. ¹² Of the patients who reach the cathlab, there is recent data that initiation of mechanical circulatory support using micro-axial pumps, such as Impella device, at the outset, referred to as the door-to-support time, may improve the outcome of these very high risk CS patients. ¹³ Some patients require the combined use of VA-ECMO and Impella, although the selection criteria for such an approach remain unclear. ¹⁴ These therapies are very complex, involve different nature of complications, and are labour and cost-intensive. Development of shock centres and extracorporeal cardio-pulmonary resuscitation (ECPR) teams in certain centres in the West is along these concepts. ¹⁵Their availability and applicability in resourceconstrained environments is uncertain. There is also need for therapeutic hypothermia and care management by a cardiologist with intensive care expertise. There is data that having a closed cardiac intensive care unit (ICU) led by a cardiac intensivist improves survival in such critically ill patients.^16,17 Recent literature shows an improvement in survival of patients with CS undergoing revascularisation who are older than75years, therefore age should not be the sole criterion for withholding revascularisation. ¹⁸ Clinical management of patients considered frail should now be stratified using different frailty classification systems developed for vulnerable population. Recently, NCDR has included Canadian Study of Health and Aging Clinical Frailty Scale to classify frailty state of patients. ¹⁹ Frailty indexes commonly utilise physical limitations of an individual assessing gait, walk patterns and weight-lossover the year, and depict biological capacity rather than chronological age.^20-22 Scoring systems, such as Fried Frailty Index (FFI),have also shown predictive value for adverse outcomes in correlation to European System for Cardiac Operative Risk Evaluation(EURO Score) and Society of Thoracic Surgeons (STS) scores, commonly used in cardiac surgery risk assessment. ²³ However, such assessments have to be carried out rapidly so that lifesaving therapies are not delayed in patients who may have an improved long term outcome after such treatment. A high proportion of patient or family refusal for revascularisation and delayed presentation were observed in the current study. Community level education to increase awareness of heart disease, its consequences and the importance of rapid early treatment is required. In environments where self-pay for healthcare is common, universal health coverage for catastrophic illness is needed so that financial considerations do not lead to a delay in life saving treatment. The limitations of the current study included data from a single centre, specialised care hospital. The patients referred here may have been felt to be more suitable for aggressive therapy and, hence, a selection bias. There may have been a greater stress on appropriate management due to being a teaching and a specialised heart care hospital. The sample size was small due to the inherent nature of the selected population. The reasons for not proceeding with revascularisation were obtained from here view of documentation in the patient records by the treating physicians and were not prospectively defined. The strengths of the study is that it was an all-outcome, comprehensive prospective, well-defined and maintained database with individual chart review and verification of details. This study for the first time highlights the various reasons due to which certain CS patients are under-treated and do not undergo revascularisation. Understanding these reasons bring up the care needs of these critically ill patients, who have a very high early mortality and whose percentage in the general community is likely higher than reported here. This study identifies multiple opportunities for improvement in the health system, including services that do not often exist in South Asia, such as cardiac ICU, cardiac intensivist, ECMO-supported cardiac resuscitation and micro-axial pumps. Additionally, denial of aggressive therapy based on futility in old age and frail status or refusal by patient or family were the other reasons, stressing the need for community-level awareness, availability of universal health coverage and objective assessment of frailty and biological age.

Conclusion

Cardiogenic shock complicating myocardial infarction not treated by revascularisation had a very poor early outcome. In the two-third of patients before treatment was initiated, there was cardiac arrest with failed resuscitation or poor recovery.

Disclaimer: None.

Conflict of Interest: None.

Source of Funding: None.

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