Cardiovascular and renal mechanisms in internal medicine
Cardiovascular assessment
Coronary Artery Disease
Core concepts
Coronary artery disease includes stable obstructive disease, plaque rupture or erosion causing acute coronary syndrome, and microvascular or vasospastic angina. Candidates must distinguish supply-demand ischemia from acute plaque rupture, interpret high-sensitivity troponin kinetics against the 99th percentile, and recognize that one normal ECG does not exclude ACS. Risk stratification combines symptoms, ECG, troponin, renal function, bleeding risk, and comorbidities. Revascularization decisions depend on anatomy, ischemic burden, symptoms despite medical therapy, and left ventricular function. Antiplatelet therapy and high-intensity statin therapy are foundational after ACS.
Question traps
A common trap is calling any troponin elevation a myocardial infarction when demand ischemia, myocarditis, pulmonary embolism, or CKD is present. Another is missing atypical presentations in women, older adults, and patients with diabetes. Do not overrely on exercise testing in patients with known CAD or an uninterpretable ECG. Post-PCI chest pain requires consideration of stent thrombosis. Do not delay reperfusion for STEMI to obtain nonessential tests.
Worked example / rule of thumb
A patient with chest pressure and negative serial troponins still requires assessment of the symptom trajectory and the validated assay pathway. Negative troponins do not by themselves establish stable angina or exclude unstable angina. If pretest probability is intermediate and there is no known CAD, coronary CT angiography is a reasonable first test; with known CAD or high risk, functional testing or invasive angiography may be preferred. Rule: treat the patient and the trajectory, not the single troponin.
Critical Care and Perioperative Cardiology
Core concepts
Critical care cardiology covers shock, respiratory failure, arrhythmia management, mechanical circulatory support, and perioperative risk. Cardiogenic shock requires rapid identification of congestion and hypoperfusion, early revascularization in ACS, and careful vasopressor or inotrope selection. Perioperative evaluation uses clinical risk indices, functional capacity, and surgery-specific risk. Postoperative troponin elevation must be interpreted with symptoms, ECG, and hemodynamics. Bedside echocardiography helps distinguish cardiogenic, septic, obstructive, and hypovolemic shock.
Question traps
Do not use pulmonary artery catheters routinely without a question they can answer. Avoid fluid boluses in cardiogenic shock with pulmonary edema. Perioperative beta blockade is not routine and can cause hypotension or bradycardia. Do not delay STEMI reperfusion for preoperative clearance. Distinguish septic from cardiogenic shock using bedside echo, lactate, and perfusion findings. Postoperative MI can be silent and atypical.
Worked example / rule of thumb
A patient with acute MI, hypotension, cool extremities and pulmonary edema requires rapid assessment and appropriate reperfusion and circulatory support. Congestion argues against indiscriminate fluid loading. Vasoactive and mechanical support choices depend on perfusion, rhythm, ventricular function and response; a fixed combination is not mandatory for every patient. Rule: shock is a perfusion diagnosis, not a blood pressure number.
Renal and electrolyte assessment
Renal assessment separates acute change from chronic impairment and examines glomerular, tubular, interstitial and obstructive mechanisms. A creatinine concentration is interpreted with baseline values, time course, muscle mass, medications and the actual clinical trajectory. Oliguria, electrolyte disturbance or pulmonary edema can create urgency even before a disease label is finalized. A renal replacement decision is not based solely on crossing one creatinine value; reversibility, refractory complications and the overall physiological state matter.
Nephritic and nephrotic patterns are useful syndromic distinctions. Hematuria with an active sediment, hypertension and declining filtration suggests a different set of mechanisms from marked protein loss with hypoalbuminemia and edema. Those patterns overlap and do not replace a relevant biopsy or etiological workup. White-cell casts and a recent drug exposure can raise concern for interstitial disease, while urinary eosinophils are not a uniquely diagnostic test. Fractional sodium excretion is affected by diuretics, chronic disease and several acute renal conditions, so a low or high value cannot independently establish the cause.
Cardiorenal reasoning connects effective perfusion, venous congestion, filtration pressure, drug effects and fluid balance. An edematous patient may still have poor effective arterial circulation. A rise in creatinine after a treatment needs interpretation rather than automatic attribution to one mechanism. Renin-angiotensin-system drugs, diuretics and other therapies have indications and monitoring requirements that depend on the actual disease, potassium, pressure and renal response. Severe hyperkalemia with ECG changes requires urgent cardiac-protection and potassium-management assessment; stabilizing the membrane does not itself remove potassium from the body.
Electrolyte disorders require both a cause and a safe correction strategy. Serum sodium reflects water balance relative to solute rather than total body sodium alone. Symptom severity, duration, risk factors and ongoing losses influence treatment and monitoring. A fixed correction limit cannot substitute for individual assessment or protect every patient from overshoot. Chronic kidney disease can also affect erythropoietin production, phosphate handling and vitamin-D activation, linking anemia and mineral-bone abnormalities to distinct physiological pathways.