What does an ECG showing sinus bradycardia, an axis of -45 degrees, and delayed precordial R wave progression indicate in an elderly woman?

ECG Interpretation: Sinus Bradycardia, Left Axis Deviation (-45°), and Delayed Precordial R Wave Progression

This ECG pattern in an elderly woman indicates three distinct findings that require systematic evaluation: a slow heart rate originating from the sinus node, left anterior fascicular block (LAFB), and possible anterior myocardial pathology or technical/positional factors—each requiring specific assessment for symptoms, structural heart disease, and coronary artery disease. 1

Understanding Each ECG Component

Sinus Bradycardia

• Sinus bradycardia means the heart rate is below 60 beats per minute with normal sinus node origin 1
• In elderly patients, this can be physiologic (normal aging, increased vagal tone) or pathologic (sinus node dysfunction, medications) 1
• Treatment is rarely indicated based solely on heart rate below an arbitrary cutoff in asymptomatic patients 2
• The key distinction is whether symptoms are directly attributable to the slow heart rate (syncope, presyncope, dizziness, heart failure symptoms, or confusion from cerebral hypoperfusion) 1

Axis of -45 Degrees (Left Anterior Fascicular Block)

• An axis between -45° and -90° defines left anterior fascicular block (LAFB), which requires QRS duration <120 ms, qR pattern in lead aVL with R-peak time ≥45 ms, and rS pattern in leads II, III, and aVF 1
• LAFB indicates conduction delay through the anterior fascicle of the left bundle branch system 1
• Isolated LAFB in asymptomatic patients typically requires no specific treatment but warrants evaluation for underlying structural heart disease 3

Delayed Precordial R Wave Progression

• Poor R wave progression suggests four major possibilities: anterior myocardial infarction, left ventricular hypertrophy, right ventricular hypertrophy, or a normal variant with diminished anterior forces 4
• When R waves decrease rather than increase across precordial leads (reversed R wave progression), this is highly specific for cardiac disease, particularly ischemic heart disease with left anterior descending artery stenosis (found in 58% of cases) 5
• This finding mandates echocardiography to assess left ventricular systolic function and wall motion abnormalities 2

Clinical Significance in an Elderly Woman

Immediate Assessment Priorities

• Determine if the patient has symptoms attributable to bradycardia: syncope, presyncope, transient dizziness, heart failure symptoms, or confusional states from cerebral hypoperfusion 1
• Review all medications that can cause or exacerbate bradycardia (beta-blockers, calcium channel blockers, digoxin, antiarrhythmics) and discontinue or reduce doses if clinically feasible 2
• Assess for reversible causes: hypothyroidism, electrolyte abnormalities, sleep apnea, increased vagal tone 1

Required Diagnostic Workup

• Obtain transthoracic echocardiography to exclude structural heart disease, assess for anterior wall motion abnormalities, evaluate left ventricular function, and look for left ventricular hypertrophy 2, 3
• Consider stress testing to assess for ischemic heart disease as the underlying cause of poor R wave progression and to evaluate chronotropic competence if symptoms occur with exertion 2, 3
• Ambulatory ECG monitoring should be strongly considered even in asymptomatic patients with conduction system disease to document suspected higher-degree AV block or intermittent bradycardia 3

Advanced Imaging Considerations

• If echocardiography is inconclusive and infiltrative disease is suspected, obtain cardiac MRI to evaluate for conditions like sarcoidosis or amyloidosis that can cause both conduction abnormalities and myocardial changes 2, 3
• Infiltrative cardiomyopathies can cause conduction disease before overt structural changes appear on standard echocardiography 3

Management Algorithm

For Asymptomatic Patients

• No pacing or pharmacologic therapy is indicated for isolated sinus bradycardia and LAFB in the absence of symptoms 2
• Regular clinical and ECG follow-up with frequency determined by underlying heart disease 3
• Patient education about symptoms that should prompt immediate evaluation (syncope, presyncope, severe fatigue, dyspnea) 1

For Symptomatic Patients

• If symptoms are clearly attributable to bradycardia: permanent pacing may be indicated per ACC/AHA/HRS guidelines 1
• Exercise stress testing can assess chronotropic competence if symptoms occur with exertion 2
• Electrophysiologic study is reasonable for patients with symptoms suggestive of intermittent bradycardia where ambulatory monitoring has not documented the arrhythmia 3

Critical Pitfalls to Avoid

• Do not assume poor R wave progression is benign—it requires echocardiography to exclude anterior myocardial infarction or other structural heart disease 2, 4, 5
• Do not use atropine for chronic management of sinus bradycardia; it has no role in chronic therapy and should not delay definitive treatment when needed 2
• Do not miss the combination of conduction abnormalities and poor R wave progression, which should prompt thorough evaluation for infiltrative cardiomyopathies requiring specific therapies beyond pacing 2, 3
• Do not rely solely on resting ECG—ambulatory monitoring is essential to exclude intermittent high-degree AV block, especially with extensive conduction system disease 3
• Do not overlook reversible causes: medications, electrolyte abnormalities, hypothyroidism, and sleep apnea must be systematically excluded 1, 2