How do I interpret an electrocardiogram (EKG) for a patient with hypertension, diabetes, hypercholesterolemia, and a history of smoking?

How to Read an EKG: A Systematic Approach for Cardiovascular Risk Assessment

Essential Role of the ECG in Hypertensive Patients

A 12-lead ECG is mandatory for all patients with hypertension and should be obtained as part of the initial routine work-up, regardless of blood pressure control status. 1, 2

The ECG serves three critical functions in your patient population:

• Detects left ventricular hypertrophy (LVH), which independently predicts cardiovascular events and mortality 1, 2
• Screens for atrial fibrillation, a common hypertensive complication requiring different management 1
• Establishes a baseline for future comparison and guides need for echocardiography 1, 2

Systematic ECG Interpretation Framework

Step 1: Rate and Rhythm Assessment

• Calculate heart rate: Count large boxes between R waves (300÷number of boxes) or use the 300-150-100-75-60-50 method 3, 4
• Assess rhythm regularity: Measure R-R intervals; irregular rhythm suggests atrial fibrillation 1, 4
• Identify P waves: Absent P waves with irregular rhythm confirms atrial fibrillation 4
• Normal heart rate: 60-100 beats/minute; tachycardia >80 bpm increases cardiovascular risk in hypertensive patients 1

Step 2: Axis Determination

• Normal axis: -30° to +90° 4
• Left axis deviation: Suggests left ventricular hypertrophy or left anterior fascicular block 4
• Use leads I and aVF: Both positive = normal axis; lead I positive + aVF negative = left axis deviation 4

Step 3: Critical Assessment for Left Ventricular Hypertrophy

This is the most important finding in hypertensive patients with diabetes. 1

Sokolow-Lyon Criteria (most commonly used):

• S wave in V1 + R wave in V5 or V6 ≥38 mm indicates LVH 1

Cornell Voltage Criteria:

• R wave in aVL + S wave in V3 >2440 mm·ms (men) or >2040 mm·ms (women) 1

Clinical significance: LVH detection mandates echocardiography for detailed structural assessment and justifies more aggressive blood pressure targets 1, 2

Step 4: Ischemia and Infarction Detection

ST Segment Analysis:

• ST elevation ≥1 mm in two contiguous leads: Suggests acute myocardial infarction requiring emergent reperfusion 5
• ST depression ≥0.5 mm: Indicates subendocardial ischemia or demand mismatch 5
• Horizontal or downsloping ST depression: More specific for ischemia than upsloping 1, 5

Q Wave Assessment:

• Pathologic Q waves (≥0.04 seconds wide or >25% of R wave height): Suggest prior myocardial infarction 1
• Poor R wave progression (R wave fails to increase from V1 to V4): May indicate anterior infarction or LVH 6

T Wave Changes:

• Deep T wave inversions in precordial leads: Suggest ischemia or prior infarction 5
• Peaked T waves: May indicate hyperkalemia (critical in diabetics on ACE inhibitors/ARBs) 4

Step 5: Conduction Abnormalities

• PR interval >200 ms: First-degree AV block 4
• QRS duration >120 ms: Bundle branch block (affects ST-T interpretation) 4
• Left bundle branch block: Makes ischemia detection unreliable; consider alternative testing 1

Clinical Decision-Making Based on ECG Findings

When ECG Shows LVH or Abnormalities:

Proceed directly to echocardiography to evaluate:

• Left ventricular mass index (abnormal if >115 g/m² in men, >95 g/m² in women) 6
• Diastolic function parameters (E/e' ratio ≥13 suggests elevated filling pressures) 6
• Regional wall motion abnormalities suggesting silent infarction 6

When ECG Shows Poor R Wave Progression:

Do NOT proceed to stress testing or coronary angiography first 6

• Obtain echocardiography to assess for LVH, diastolic dysfunction, or silent MI 6
• Routine coronary screening in asymptomatic diabetics does not improve outcomes 6

When ECG Shows ST-T Wave Changes:

• With active chest pain: Triage for emergent cardiac catheterization if ST elevation present 5
• Without symptoms: Compare to prior ECGs; may represent LVH strain pattern or prior infarction 1, 5

Common Pitfalls to Avoid

Do not interpret ST-T changes in isolation without considering:

• LVH (causes strain pattern mimicking ischemia) 1, 5
• Bundle branch blocks (invalidate ST-T interpretation) 1
• Comparison to previous ECGs (essential for detecting acute changes) 3, 5

Do not skip ECG in "controlled" hypertension: LVH may be present despite blood pressure control and requires detection for risk stratification 2

Do not order stress testing before echocardiography in asymptomatic patients with ECG abnormalities and diabetes 6

Integration with Overall Risk Assessment

Your patient's cardiovascular risk is determined by:

• Age >65 years (high risk) 1
• Diabetes mellitus (high risk) 1
• Smoking history (high risk, especially with diabetes interaction) 1, 7, 8
• Hypercholesterolemia (high risk) 1, 7
• ECG-detected LVH (elevates to very high risk) 1

This patient likely has 71-86% pretest probability of significant coronary disease based on age, diabetes, smoking, and hyperlipidemia 1