Cardiac Anatomy and Function

Left Ventricle and Atrial Structure

The basal anterolateral segment of the left ventricle is the portion of the left ventricular free wall between the anterior and inferolateral segments at the base of the heart, while the mid anterolateral segment is similarly positioned at the mid-ventricular level, as described by the American College of Cardiology 1
The left atrial appendage (LAA) is a finger-like extension of the anterolateral left atrial wall located in the left atrioventricular groove, according to the European Heart Journal 2
Left atrial enlargement often occurs along the superoinferior axis more prominently than the anteroposterior axis, as reported by the European Heart Journal 2

Abnormal LA function is characterized by decreased compliance and/or contractile dysfunction, according to the European Heart Journal 2
The LAA in the anterolateral region is a common site for thrombus formation in atrial fibrillation, as noted by the European Heart Journal 2

Ventricular mechanisms for secondary mitral regurgitation include LV dysfunction and enlargement, focal wall motion abnormalities affecting the anterolateral region, and abnormal tethering geometry due to papillary muscle dysfunction, as described by the JACC: Heart Failure 3

Echocardiography, including transthoracic and transesophageal echocardiography, can be used for assessment of wall motion abnormalities, and speckle-tracking echocardiography can be used for strain analysis of the anterolateral segments, according to Circulation 4
Cardiac CT provides high spatial resolution for assessment of anterolateral structures, is excellent for quantification of epicardial adipose tissue, and allows visualization of left atrial appendage morphology, as reported by Circulation and the European Heart Journal 2, 4
Cardiac MRI can be used for tissue characterization for fibrosis or infarction, cine sequences for functional assessment, and tissue tracking for strain analysis, according to Circulation 4

Epicardial adipose tissue in the anterolateral region may serve as a source of proinflammatory cytokines, contributing to fibrotic remodeling of the atrial myocardium, as noted by Circulation 4

5, 6, 7

New left bundle branch block (LBBB) is no longer considered diagnostic of STEMI in isolation but should be considered in LBBB with specific ST-segment criteria, including ST elevation ≥1 mm concordant with QRS complex, ST depression ≥1 mm in leads V1-V3, or ST elevation ≥5 mm discordant with QRS complex, as noted by the American College of Cardiology and the American Heart Association 8, 9

Right ventricular infarction should be suspected in patients with inferior STEMI who present with hypotension, jugular venous distention, clear lung fields, and Kussmaul's sign (paradoxical rise in jugular venous pressure during inspiration) 10
ST elevation >0.05 mV (>0.1 mV in men <30 years old) in V4R is highly specific for RV infarction, and these leads should be recorded immediately when inferior STEMI is identified 11, 12
Obtain a 12-lead ECG within 10 minutes of first medical contact, adding right-sided leads (V3R-V4R) and posterior leads (V7-V9) to confirm right ventricular and posterior involvement, as patients with multi-territory infarction are at high risk for cardiogenic shock, according to the American College of Cardiology and the American Heart Association 9, 8, 12

The American College of Cardiology suggests that management differs significantly for RV infarction, requiring preload maintenance and avoidance of nitrates, and right-sided leads should be obtained early to guide management strategies 10
Primary PCI is the preferred reperfusion strategy for multi-territory infarction, with a target door-to-balloon time of <90 minutes, according to the American College of Cardiology 9
If PCI is not available within 120 minutes, consider fibrinolytic therapy in the absence of contraindications, as the "time is muscle" principle is especially critical in multi-territory infarction, according to the American Heart Association 9
Administer antiplatelet therapy, including aspirin 162-325 mg loading dose and a P2Y12 inhibitor (preferably ticagrelor or prasugrel if no contraindications), as suggested by the American College of Cardiology 13
Administer anticoagulation, such as unfractionated heparin, enoxaparin, or bivalirudin, per institutional protocol, as recommended by the American College of Cardiology 13
Maintain preload with IV fluids if hypotensive and avoid nitrates and other preload reducers in patients with right ventricular infarction, as they are at high risk for cardiogenic shock, according to the American College of Cardiology 9

Early recognition of RV infarction is critical, as it complicates approximately 25% of inferior MIs, and patients with RV involvement have worse prognosis and higher mortality 10
Multi-territory ST elevation carries a higher risk of cardiogenic shock, malignant arrhythmias, mechanical complications, and in-hospital mortality, according to the American Heart Association 9
In-hospital mortality in unselected patients with STEMI varies between 4-12%, and the implementation of standardized STEMI care networks with protocols has significantly contributed to reducing time to reperfusion therapy and associated mortality, according to the European Society of Cardiology and the American College of Cardiology 14, 13
Continuous cardiac monitoring should be performed to detect potentially life-threatening arrhythmias, and oxygen should be administered only if SaO₂ <90%, as recommended by the American College of Cardiology 14