The 12 lead ECG rules the waves in acute cardiovascular care

Although a wide array of very sophisticated diagnostic techniques is available to the modern cardiologist, the basic 12 lead electrocardiogram (ECG) remains the cornerstone in the clinical assessment of acute cardiac syndromes in the prehospital setting, in the emergency department, in the intensive cardiac care unit and in the hospital ward. In acute coronary syndromes (ACS) the 12-lead ECG is the first line diagnostic test that needs to be recorded within 10 minutes after the first medical contact.1, 2 Especially in the assessment of patients with a suspected ST segment elevation myocardial infarction (STEMI) the initial 12 lead ECG plays a pivotal role as it triggers the decision to send the patients for urgent primary percutaneous intervention (PCI). Although the diagnostic algorithms for automated computerized interpretation of the ECG have improved considerably there remain frequent incorrect readings of arrhythmias, conduction disorders and pacemaker rhythms and a wide variation in the diagnostic accuracy in the identification of STEMI.3 Proficiency in rapid and accurate ECG interpretation remains therefore a necessary skill for all cardiologists and all allied professions working in acute cardiac care. Moreover, although the ECG is already there for 100 years, it remains important to develop and to assess new diagnostic criteria and to relate specific ECG patterns with clinical conditions and their outcomes in order to further improve the diagnostic accuracy and clinical utility of this readily and universally available bedside examination technique. In this issue a special focus is on specific ECG features and on the role of the basic 12 lead ECG in different acute cardiovascular diseases. An ACS due to a critical left main stenosis is a dreadful clinical condition that necessitates early identification and urgent revascularization in order to avoid lethal extensive myocardial necrosis. The presence of widespread ST depression and ST-segment elevation in aVR is the classic ECG feature of extensive myocardial ischemia related to a critical left main stenosis or occlusion4 that should prompt a primary PCI strategy.5 Although ST segment elevation in aVR is a sensitive ECG criterion for the detection of left main ACS it appears less powerful as prognostic predictor. A retrospective analysis of consecutive patients with left main ACS showed that ST-segment elevation in lead aVL rather than aVR, width of the QRS-complex at lead V3 and number of ST-segment elevation were prognostic predictors for in-hospital mortality.6 Whether a new score including these ECG features performs better in outcome prediction than the clinical GRACE risk score needs to be validated further in a large prospective series. The presence of a left bundle branch block (LBBB) makes the ECG diagnosis of a STEMI difficult. The latest ESC guidelines on the management of STEMI recommend to manage patients with suspected ongoing myocardial ischemia and a LBBB in a manner similar to STEMI patients.2 As only 5 to 7% of chest pain patients presenting with a LBBB to the emergency department finally will be diagnosed as acute myocardial infarction7 this recommendation may lead to a great number of unnecessary activations of the catheterization laboratory or worse of potential harmful fibrinolytic treatments. Based on the analysis of a group of chest pain patients with a LBBB selected from a large prospective series of patients referred for primary PCI a new hierarchical diagnosis and treatment algorithm was proposed.8 This algorithm based on the presence of hemodynamic instability, the application of the Sgarbossa concordance criteria and the results of serial cardiac biomarker testing and/or of a limited bed side echocardiography yielded a high sensitivity (97%) and negative predictive value (94%) for the identification of a culprit lesion. The development of a complete atrioventricular block in patients with an ACS is an ominous sign as it is associated with an increased risk of cardiogenic shock, heart failure, ventricular arrhythmias, mechanical complications and death during hospitalization. A large contemporary series of patients hospitalized with an ACS showed that despite a much lower incidence of complete atrioventricular block in the primary PCI era, this conduction disorder is still associated with an increased risk of complications.9 The negative impact on prognosis of the development of atrioventricular conduction disorders is also confirmed by the results of the Spanish ARIAM registry.10 ACS patients who needed a permanent pacemaker implantation showed a tenfold increased mortality risk. Takotsubo cardiomyopathy can masquerade as STEMI with anginal chest pain, ST-segment elevation, and elevated cardiac biomarkers. Although the ST segment elevation pattern frequently is indistinguishable from that of STEMI, several ECG features suggestive for Takotsubo cardiomyopathy have been described. A case is presented of postoperative Takotsubo cardiomyopathy with various electrocardiographic features that should raise suspicion for this syndrome.11 A meta-analysis showed that patients with a spontaneous subarachnoid hemorrhage may develop a Takotsubo syndrome in 4,4% and that this complication is associated with a 2 to 3 fold increase of in-hospital mortality.12 Patients with a spontaneous subarachnoid hemorrhage should therefore be screened for the presence of the typical ECG and echocardiographic features of the Takotsubo syndrome. A burst of reperfusion ventricular arrhythmias (ventricular premature beats with long coupling intervals and accelerated idioventricular rhythms) is frequently observed after recanalization by primary PCI. In the era of coronary thrombolysis these ventricular arrhythmias were considered to be a ECG marker of successful reperfusion. However, in a study of STEMI patients in whom infarct size and microvascular obstruction was assessed by cardiac magnetic resonance imaging a burst of reperfusion ventricular arrhythmias was associated with a much greater infarct size.13 The increased infarct size was only observed in the group of patients with an optimal TIMI 3 epicardial blood flow and no microvascular obstruction. It appears therefore that a burst of reperfusion ventricular arrhythmias is an independent marker of additional myocardial reperfusion injury. The observation of these arrhythmias should therefore raise the clinical awareness that the patient will develop a greater than normal infarct size and therefore may have an increased risk for heart failure complications. A stroke may be the first manifestation of atrial fibrillation (AF). Guidelines for the UK emergency medical system recommend therefore to register a 12 lead ECG in the prehospital environment. A systematic literature review shows that ECG abnormalities are common in hospitalized stroke patients but that there is insufficient evidence on the use of the 12 lead ECG in the prehospital setting.14 AF was significantly more prevalent in ischemic stroke and was associated with a two-fold increase of three-month mortality. In patients with AF the CHA2DS2-VASc score is commonly used for assessing the risk of stroke and thromboembolism and to determine the necessity of anticoagulant therapy. It has been suggested that the score also can be used to predict stroke complications in ACS. In a meta-analysis, performed on more than half a million patients with a recent ACS, every single risk factor included in the CHA2D2-VASc score retained its association with stroke and/or transient ischemic attack despite a low prevalence of AF (11.2%) in this population.15 These findings seem to confirm that the CHA2D2-VASc score also can be used to assess the stroke risk in patients with an ACS irrespective of the presence of AF. However, the absence of AF on a single baseline 12 lead ECG recording does not exclude its presence in paroxysmal form. Furthermore, all components of the CHA2D2-VASc score are also risk factors for AF development. ACS patients are at high risk of arrhythmia development and AF frequently remains undiagnosed and untreated in this population. Therefore, every effort should be made to keep looking for AF in ACS patients to allow clinicians to provide a guided patient-tailored therapy.16 Patients visiting the emergency department for chest pain in whom acute myocardial infarction (MI) had been ruled out by history, 12 lead ECG and serial high-sensitivity troponin measurements may be discharged early from emergency department without further hospitalization.1 It has been recommended to perform predischarge exercise ECG testing before discharge in order to detect ischemic heart disease.17 In a large study in chest pain patients in whom acute MI had been ruled out predischarge exercise ECG testing did not predict subsequent death or MI during follow-up up to one year.18 Furthermore, the risks of death and MI in the study patients were comparable to a matched Swedish population. These findings suggest that pre-discharge exercise ECG testing may be omitted as these patients a constitute low risk population. The advent of high-sensitivity troponins apparently allows more selective testing and simpler assessment that promises increased benefits of shorter length of stay and improved resource utilization without limiting patient safety.19 In this issue we start with a new initiative. The journal will regularly publish invited educational review papers on important topics in acute cardiovascular care. In this issue we are focusing on the management of elderly patients with acute coronary syndrome.20