Non-ST-elevation myocardial infarction (NSTEMI)

ST-elevation myocardial infarction is acute transmural myocardial ischemia from complete coronary occlusion, diagnosed by ischemic symptoms with diagnostic ST-segment elevation and a rising troponin. It is a time-critical emergency in which immediate reperfusion, primary PCI within 90 minutes or fibrinolysis when PCI is unavailable, plus antiplatelet and anticoagulant therapy, determines survival.

Unstable angina is acute myocardial ischemia from a non-occlusive coronary thrombus causing rest, new, or crescendo angina without a troponin rise, placing it on the acute coronary syndrome spectrum just short of NSTEMI. Diagnosis is clinical with ischemic ECG changes and negative serial troponins, and management mirrors NSTE-ACS with antithrombotic therapy and risk-guided angiography.

Chronic stable angina is reproducible, exertional chest discomfort from fixed coronary stenosis causing demand-related ischemia, relieved by rest or nitroglycerin. Diagnosis combines the typical anginal pattern with stress testing or coronary imaging, and treatment is antianginal and secondary-prevention medical therapy, with revascularization for refractory symptoms or high-risk anatomy.

Acute heart failure is the rapid onset or worsening of heart failure symptoms requiring urgent therapy, most often pulmonary congestion from a precipitant such as ischemia, arrhythmia, or nonadherence. Management is oxygen, intravenous diuretics, and vasodilators for the congested-but-perfused patient, with inotropes or support for the hypoperfused patient.

Aortic dissection is a tear in the aortic intima allowing blood to split the media, creating a false lumen, and is a surgical emergency. Type A (ascending) dissection needs emergency surgery, while type B (descending) is usually managed medically with rapid heart-rate and blood-pressure control; the priority is impulse control with a beta-blocker first.

Pulmonary embolism is thrombus, usually from a lower-extremity deep vein thrombosis, obstructing the pulmonary arterial circulation and causing V/Q mismatch, right ventricular strain, and hypoxemia. Diagnosis follows Wells criteria (with PERC in low-risk patients) to sequence D-dimer, CT pulmonary angiography, and V/Q scanning, and management is risk-stratified anticoagulation escalating to thrombolysis or embolectomy for hemodynamic instability.

Myocarditis is inflammation of the myocardium, most often postviral or immune-mediated, presenting across a spectrum from a mild chest-pain syndrome mimicking myocardial infarction to fulminant heart failure and arrhythmia. Diagnosis relies on cardiac MRI (or biopsy for severe or refractory cases), and treatment is supportive heart-failure care, with cause-specific immunosuppression for giant cell, checkpoint-inhibitor, and autoimmune myocarditis.

Acute pericarditis is inflammation of the pericardium, most often viral or idiopathic, presenting with pleuritic chest pain relieved by sitting forward, a pericardial friction rub, and diffuse ST elevation with PR depression. Treatment is an NSAID plus colchicine, and the main hazards are effusion, tamponade, and recurrence.

GERD is retrograde reflux of gastric contents into the esophagus causing heartburn and regurgitation, diagnosed clinically and confirmed by response to an empiric PPI trial, with endoscopy reserved for alarm features or refractory symptoms. Management proceeds from lifestyle measures through an 8-week once-daily PPI trial, dose escalation or agent switch for partial response, and fundoplication for medication-refractory or regurgitation-predominant disease.