Clinical and Prognostic Value of the Electrocardiogram in Patients With Acute Occlusion of the Left Circumflex Coronary Artery

Context-independent identification of myocardial ischemia in the prehospital ECG of chest pain patients

Non-traumatic chest pain is a frequent reason for an urgent ambulance visit of a patient by the emergency medical services (EMS). Chest pain (or chest pain-equivalent symptoms) can be innocent, but it can also signal an acute form of severe pathology that may require prompt intervention. One of these pathologies is cardiac ischemia, resulting from a disbalance between blood supply and demand. One cause of a diminished blood supply to the heart is acute coronary syndrome (ACS, i.e., cardiac ischemia caused by a reduced blood supply to myocardial tissue due to plaque instability and thrombus formation in a coronary artery). ACS is dangerous due to the unpredictable process that drives the supply problem and the high chance of fast hemodynamic deterioration (i.e., cardiogenic shock, ventricular fibrillation). This is why an ECG is made at first medical contact in most chest pain patients to include or exclude ischemia as the cause of their complaints. For speedy and adequate triaging and treatment, immediate assessment of this prehospital ECG is necessary, still during the ambulance ride. Human diagnostic efforts supported by automated interpretation algorithms seek to answer questions regarding the urgency level, the decision if and towards which healthcare facility the patient should be transported, and the indicated acute treatment and further diagnostics after arrival in the healthcare facility. In the case of an ACS, a catheter intervention room may be activated during the ambulance ride to facilitate the earliest possible in-hospital treatment. Prehospital ECG assessment and the subsequent triaging decisions are complex because chest pain is not uniquely associated with ACS. The differential diagnosis includes other cardiac, pulmonary, vascular, gastrointestinal, orthopedic, and psychological conditions. Some of these conditions may also involve ECG abnormalities. In practice, only a limited fraction (order of magnitude 10%) of the patients who are urgently transported to the hospital because of chest pain are ACS patients. Given the relatively low prevalence of ACS in this patient mix, the specificity of the diagnostic ECG algorithms should be relatively high to prevent overtreatment and overflow of intervention facilities. On the other hand, only a sufficiently high sensitivity warrants adequate therapy when needed. Here, we review how the prehospital ECG can contribute to identifying the presence of myocardial ischemia in chest pain patients. We discuss the various mechanisms of myocardial ischemia and infarction, the typical patient mix of chest pain patients, the shortcomings of the ST-elevation myocardial infarction (STEMI) and non-ST-elevation myocardial infarction (NSTEMI) ECG criteria to detect a completely occluded culprit artery, the OMI ECG criteria (including the STEMI-equivalent ECG patterns) in detecting completely occluded culprit arteries, and the promise of neural networks in recognizing ECG patterns that represent complete occlusions. We also discuss the relevance of detecting any ACS/ischemia, not necessarily caused by a total occlusion, in the prehospital ECG. In addition, we discuss how serial prehospital ECGs can contribute to ischemia diagnosis. Finally, we discuss the diagnostic contribution of a serial comparison of the prehospital ECG with a previously made nonischemic ECG of the patient.

The CineECG in ischemia localization in ST-elevation (equivalent) acute coronary syndromes

AIM OF THE STUDY

In this proof of concept study we aimed to visualize and quantify the injury vectors using the CineECG in representative examples of ST elevation acute myocardial infarction (STEMI) and STEMI-equivalent electrocardiograms (ECG's). For this purpose ECG's were selected with different ST deviation patterns in acute anterior wall, inferior or posterolateral wall infarctions.

METHODS

The ST-amplitudes of the individual leads were measured between J-point and 60 ms after the J-point. These data were used to compute the direction and size (i.e. ST-amplitudes) of the injury vectors of the respective STEMI (equivalent)'s and displayed in the frontal, transverse and sagittal view. The relative contribution of the ST vector was computed for each axis (X,Y,Z) and per view using the length of the projected ST vector on the respective plane.

RESULTS

The injury vectors accurately pointed to the area at risk in either proximal, mid or distal occlusions of the respective coronary arteries. Moreover in LCX occlusions, where no or small ST abnormalities in the standard ECG were present, the CineECG was found to be capable in pointing towards the ischemic area. Especially the visualization of the ST-vector in the sagittal plane was found to be contributing.

CONCLUSIONS

These findings suggest that the CineECG could become a useful additional tool to support the clinician. Moreover our preliminary findings suggest that CineECG may be more capable in detecting ischemic changes in situations where the ECG is not supportive, such as in LCX occlusions. Further studies in patient cohorts are needed to confirm these observations.

Left circumflex STEMI presenting as de Winter sign, an ECG Zebra that gives you the chills! A case report

de Winter ECG sign is an anterior ST-segment elevation myocardial infarction equivalent, which refers to an occlusion of the proximal left anterior descending (LAD) coronary artery with tall T waves and the absence of ST elevations in the precordial leads on the electrocardiogram (ECG). This sign is often under-recognized and not treated as an ST-segment elevation myocardial infarction which can increase the morbidity and mortality of such a life-threatening condition. Here we report a characteristic de Winter ECG sign involving left circumflex artery as culprit vessel, which was managed with PCI.

Influence of Left Bundle Branch Block on the Electrocardiographic Changes Induced by Acute Coronary Artery Occlusion of Distinct Location and Duration

Background: Electrocardiographic (ECG) diagnosis of acute myocardial ischemia is hampered in the presence of left bundle branch block (LBBB).

Objectives: We analyzed the influence of location and duration of myocardial ischemia on the ECG changes in pigs with LBBB.

Methods: LBBB was acutely induced in 14 closed chest anesthetized pigs by local electrical ablation. Thereafter, episodes of 5 min catheter balloon occlusion followed by 10 min reperfusion of the left anterior descending (LAD), left circumflex (LCX), and right (RCA) coronary arteries were done sequentially in 5 pigs. Additionally, a 3-h occlusion of these arteries was performed separately in the other 9 pigs. A 15-lead ECG including leads V7 to V9 was continuously recorded.

Results: Ablation induced LBBB showed QRS widening, loss of r wave in V1, and predominant R waves in V2 to V9. After 5 min of ischemia the occluded artery could be identified in all cases: the LAD by R waves and ST elevation in V1–V3; the LCX by both ST segment elevation in II, III, aVF, V7 to V9 and ST segment depression in V1 to V4; and the RCA by ST depression and new S-waves in all precordial leads. Three hours after coronary occlusion, ST segment changes declined progressively and only the LAD occlusion could be reliably recognized.

Conclusion: LBBB did not mask the ECG recognition of the occluded coronary artery during the first 60 min of ischemia, but 3 h later only the LAD occlusion could be reliably identified. ST elevation in leads V7 to V9 is specific of LCX occlusion and it could be useful in the diagnosis of acute myocardial ischemia in the presence of LBBB.