Study guide
This chapter covers the three highest-yield internal medicine organ systems on Step 2 CK: cardiovascular, respiratory, and gastrointestinal disease. Together these systems account for a large share of the internal medicine/adult primary-care content and are tested heavily through next-best-step and management vignettes rather than isolated recall. Expect emphasis on acute coronary syndromes, heart failure guideline-directed therapy, pulmonary embolism workup, and the acute abdomen/GI bleeding spectrum, all framed around timely recognition and stepwise management.
Acute Coronary Syndrome and STEMI Management
Chest pain vignettes require rapid triage using ECG and troponin. ST-elevation myocardial infarction (STEMI) is diagnosed by new ST elevation or a new left bundle branch block on ECG in the appropriate clinical context, and management is time-dependent: the priority is reperfusion, either primary percutaneous coronary intervention (PCI) if available within the guideline-recommended door-to-balloon window, or fibrinolytic therapy if PCI is not accessible in time and there are no contraindications (recent hemorrhagic stroke, active bleeding, recent major surgery). Initial medical therapy classically includes aspirin, a P2Y12 inhibitor, anticoagulation, a beta-blocker (once hemodynamically stable), and a high-intensity statin; nitrates and morphine are adjuncts for symptom control but do not substitute for reperfusion. Non-ST-elevation ACS (NSTEMI/unstable angina) is managed with similar antiplatelet and anticoagulant therapy plus risk stratification to decide the timing of invasive angiography. Step 2 CK vignettes test recognition of atypical presentations (diabetics, women, the elderly), contraindications to thrombolytics, and complications such as cardiogenic shock, papillary muscle rupture, or free wall rupture presenting with a new murmur or sudden hypotension after MI. Understanding when to choose PCI versus fibrinolysis, and recognizing post-MI complications by their timing after the index event, is central to this topic.
Heart Failure and Guideline-Directed Medical Therapy
Heart failure with reduced ejection fraction (HFrEF) questions test both diagnosis (using echocardiography to confirm reduced EF, plus BNP/NT-proBNP and clinical signs like elevated JVP, S3, pulmonary crackles, and lower extremity edema) and chronic guideline-directed medical therapy (GDMT). The modern GDMT framework for HFrEF includes four pillars: a renin-angiotensin-system inhibitor (ACE inhibitor, ARB, or preferably an ARNI such as sacubitril-valsartan), a beta-blocker with proven mortality benefit (carvedilol, metoprolol succinate, or bisoprolol), a mineralocorticoid receptor antagonist (spironolactone or eplerenone), and an SGLT2 inhibitor; these are typically initiated and up-titrated together rather than sequentially withheld. Loop diuretics manage volume overload symptomatically but do not alter mortality. Acute decompensated heart failure is treated with diuresis, oxygen, and afterload reduction, while cardiogenic shock may require inotropes or mechanical support. Vignettes distinguish HFrEF from heart failure with preserved ejection fraction (HFpEF), where the therapeutic approach centers on diuretics, blood pressure control, and SGLT2 inhibitors rather than the full neurohormonal blockade pillars. Recognizing contraindications (e.g., avoiding ACE inhibitors/ARNI in hyperkalemia or angioedema history, avoiding beta-blockers in decompensated cardiogenic shock) is frequently tested.
Pulmonary Embolism: Diagnosis and Risk Stratification
Pulmonary embolism (PE) vignettes test a stepwise diagnostic algorithm. Clinical probability is first estimated using validated criteria (e.g., Wells score); low-probability patients are screened with a D-dimer, and a negative D-dimer effectively rules out PE in low-risk patients, while an elevated D-dimer or a moderate-to-high pretest probability warrants CT pulmonary angiography (CTPA) as the diagnostic study of choice. V/Q scanning is reserved for patients who cannot receive IV contrast (e.g., renal failure, contrast allergy). Once diagnosed, patients are risk-stratified: hemodynamically stable patients are anticoagulated (direct oral anticoagulants are now first-line for most patients, with important exceptions such as pregnancy, severe renal impairment, or antiphospholipid syndrome), while those with hemodynamic instability (massive PE with hypotension) require thrombolysis or embolectomy. Submassive PE with right ventricular strain but preserved blood pressure requires closer monitoring and consideration of advanced therapy. Long-term anticoagulation duration depends on whether the PE was provoked (transient risk factor, typically 3 months) versus unprovoked or associated with active malignancy (longer or indefinite therapy). Vignettes also test recognizing classic risk factors (immobilization, malignancy, recent surgery, oral contraceptives, inherited thrombophilias) and the pathophysiology of pleuritic chest pain, tachycardia, and hypoxemia.
Acute Abdomen and GI Bleeding
GI vignettes frequently test the localization and next-step management of abdominal pain and gastrointestinal bleeding. Upper GI bleeding (hematemesis, melena) is stabilized first with IV fluids and blood products as needed, followed by upper endoscopy for both diagnosis and therapy (e.g., variceal banding, ulcer clipping); proton pump inhibitor infusion and, in suspected variceal bleeding, octreotide plus prophylactic antibiotics are started empirically before endoscopy. Lower GI bleeding (hematochezia) prompts consideration of diverticulosis, angiodysplasia, or malignancy, with colonoscopy as the primary diagnostic tool once the patient is stabilized. Spontaneous bacterial peritonitis (SBP) is a key complication of cirrhotic ascites, suspected in a cirrhotic patient with fever, abdominal pain, or altered mentation; diagnostic paracentesis showing an ascitic fluid absolute neutrophil count of at least 250 cells/mm3 confirms the diagnosis, and empiric antibiotics (typically a third-generation cephalosporin) plus IV albumin (to reduce risk of hepatorenal syndrome) are indicated. Acute pancreatitis is diagnosed by two of three criteria (characteristic epigastric pain, lipase/amylase elevation, and imaging findings) and managed with aggressive IV fluid resuscitation, pain control, and early enteral feeding once tolerated, reserving imaging and intervention for complications or unclear etiology.
Colorectal and Lung Cancer Screening
Health-maintenance and preventive-care questions are heavily represented on Step 2 CK and often hinge on precise, current screening guidelines. Colorectal cancer screening in average-risk adults begins at age 45 per current guidelines, with options including colonoscopy, stool-based testing (FIT or FIT-DNA), or CT colonography, with the specific starting age and interval being a tested detail; family history of colorectal cancer or polyps shifts screening to begin earlier and with more frequent colonoscopy. Lung cancer screening with low-dose CT is recommended for patients age 50-80 with at least a 20-pack-year smoking history who currently smoke or quit within the past 15 years; vignettes test correctly identifying eligible candidates based on age and smoking history rather than performing screening on all smokers. These questions reward memorizing the specific numeric thresholds (age cutoffs, pack-year history, years since quitting) rather than general concepts, since distractors are often plausible-sounding but numerically incorrect.
Key terms
- STEMI
- — ST-elevation myocardial infarction; diagnosed by new ST elevations (or new LBBB) on ECG and managed with emergent reperfusion via PCI or fibrinolysis.
- GDMT
- — Guideline-directed medical therapy for HFrEF, comprising an ACE inhibitor/ARB/ARNI, beta-blocker, mineralocorticoid receptor antagonist, and SGLT2 inhibitor.
- Wells score
- — A clinical prediction rule used to estimate pretest probability of pulmonary embolism and guide whether D-dimer or CTPA is the appropriate next test.
- CTPA
- — CT pulmonary angiography; the imaging study of choice for diagnosing pulmonary embolism in patients who can receive IV contrast.
- Spontaneous bacterial peritonitis (SBP)
- — Infection of ascitic fluid in a cirrhotic patient, diagnosed by an ascitic fluid absolute neutrophil count of at least 250 cells/mm3 on paracentesis and treated with antibiotics plus IV albumin.
- HFrEF vs HFpEF
- — Heart failure classified by ejection fraction on echocardiography; HFrEF gets the four-pillar neurohormonal GDMT, while HFpEF management centers on diuretics, blood pressure control, and SGLT2 inhibitors.
- Provoked vs unprovoked VTE
- — A provoked venous thromboembolism has an identifiable transient risk factor and is typically treated for a shorter defined course; unprovoked or cancer-associated VTE generally requires longer or indefinite anticoagulation.
- Low-dose CT lung cancer screening
- — Preventive imaging recommended for patients age 50-80 with at least a 20-pack-year smoking history who currently smoke or quit within the past 15 years; a frequently tested numeric threshold.
Exam tips
- When a vignette gives ST elevations, your first action is reperfusion strategy selection (PCI vs. fibrinolysis based on time/availability), not just 'give aspirin and admit.'
- For HFrEF questions, remember all four GDMT pillars are typically started together and up-titrated, not added one at a time waiting for symptoms to worsen.
- In PE vignettes, use the pretest probability to decide whether D-dimer or CTPA is the next step — ordering CTPA in a low-probability patient with a negative D-dimer is a distractor trap.
- For a cirrhotic patient with fever or confusion, jump straight to diagnostic paracentesis with cell count/differential before broad-spectrum imaging.
- Memorize the exact numeric cutoffs for colorectal (age 45) and lung cancer screening (age 50-80, 20 pack-years, quit within 15 years) since distractors use slightly-off numbers.
- Distinguish post-MI complication timing: free wall rupture and papillary muscle rupture present differently and at different intervals after the infarct — use the vignette's day-count clue.