Can you interpret this ECG showing sinus tachycardia with a ventricular rate of 101 bpm, PR interval 162 ms, QRS duration 82 ms, QTc 448 ms, possible left atrial enlargement, minimal voltage criteria for left ventricular hypertrophy (Cornell product), and evidence of a prior septal infarct, with no significant change compared to a previous ECG?

ECG Interpretation: Sinus Tachycardia with Structural Findings

This ECG shows sinus tachycardia (101 bpm) with evidence of chronic structural heart disease—specifically possible left atrial enlargement, minimal voltage criteria for left ventricular hypertrophy, and a prior septal infarct—that requires clinical correlation to determine if the patient has symptomatic heart disease warranting further workup or if these are stable chronic findings. 1

Rhythm Analysis

Sinus Tachycardia (101 bpm)

• The ventricular rate of 101 bpm exceeds the normal upper limit of 100 bpm, meeting criteria for sinus tachycardia 1
• Sinus tachycardia may be appropriate (physiological response to exercise, fever, pain, dehydration, anemia, infection) or inappropriate when the heart rate exceeds what would be expected for the clinical circumstances 1
• The key clinical question is whether this tachycardia represents a physiological response to an underlying condition or reflects cardiac dysfunction requiring the elevated heart rate to maintain adequate cardiac output 1

Conduction Intervals

PR Interval: 162 ms (Normal)

• Falls within the normal range; no evidence of first-degree AV block 1
• Notably longer than the short PR interval (88 ms) that can be seen in conditions like Fabry disease with left ventricular hypertrophy 1

QRS Duration: 82 ms (Normal)

• Normal QRS duration (<120 ms) excludes bundle branch block or intraventricular conduction delay 1
• This narrow QRS during tachycardia confirms the rhythm is supraventricular in origin 1

QTc: 448 ms (Upper Normal Range)

• The corrected QT interval of 448 ms approaches but does not exceed the upper normal limit of approximately 450-460 ms in adults 1
• This borderline prolongation warrants attention to avoid adding QT-prolonging medications 2

Structural Findings

Possible Left Atrial Enlargement

• Left atrial enlargement on ECG is considered an early sign of hypertensive heart disease, even before left ventricular hypertrophy becomes apparent 3
• This finding suggests chronic pressure or volume overload of the left atrium, most commonly from hypertension, mitral valve disease, or left ventricular dysfunction 3
• Clinical correlation with echocardiography would definitively establish left atrial size and identify the underlying cause 3

Minimal Voltage Criteria for LVH (Cornell Product)

• The ECG shows minimal voltage criteria for left ventricular hypertrophy by Cornell product, which the automated interpretation notes "may be normal variant" 1
• Important pitfall: Apparent LVH voltage criteria during tachycardia can be falsely positive due to increased S-wave amplitude in precordial leads V2-V5 during rapid heart rates 4
• This tachycardia-mediated apparent LVH is unrelated to true structural hypertrophy and resolves when heart rate normalizes 4
• Given the concurrent sinus tachycardia, this minimal LVH finding should be interpreted cautiously and confirmed on a repeat ECG at normal heart rate 4

Septal Infarct (Cited on or Before Prior Date)

• The presence of a prior septal infarct indicates previous myocardial injury, most commonly from coronary artery disease affecting the left anterior descending artery 5
• This finding establishes that the patient has structural heart disease with myocardial scar, which has important implications:
  • Increased risk of ventricular arrhythmias originating from the scar tissue 5
  • Potential for reduced left ventricular function depending on infarct size 5
  • Need for optimal medical therapy for coronary artery disease and heart failure prevention 1

Clinical Significance and Management Approach

When Tachycardia Rate <150 bpm (as in this case at 101 bpm):

• The tachycardia is less likely to be the primary cause of symptoms unless there is significant ventricular dysfunction 1
• The priority is to identify and treat the underlying cause of the tachycardia rather than the tachycardia itself 1

Systematic Evaluation Required:

• Assess for reversible causes: fever, infection, dehydration, anemia, pain, hypoxemia, pulmonary embolism, hyperthyroidism 1
• Evaluate cardiac function: In patients with prior myocardial infarction and possible LVH, the elevated heart rate may represent a compensatory mechanism for reduced stroke volume 1
• Review medications: Ensure the patient is not on agents that could contribute to tachycardia or QT prolongation 2

Specific Considerations Given This ECG:

• The combination of prior septal infarct, possible left atrial enlargement, and borderline LVH suggests chronic heart disease 3
• If the patient has left ventricular dysfunction, the cardiac output may depend on maintaining an elevated heart rate as a compensatory mechanism 1
• Inappropriate rate control in this setting could worsen hemodynamics 1

Critical Pitfalls to Avoid

• Do not treat the tachycardia rate in isolation without identifying the underlying cause 1
• Do not assume the minimal LVH voltage criteria represent true hypertrophy during tachycardia—confirm with a repeat ECG at normal heart rate 4
• Do not overlook the QTc of 448 ms when prescribing new medications; avoid QT-prolonging agents 2
• Do not dismiss the prior septal infarct as irrelevant—this establishes structural heart disease with arrhythmogenic potential 5
• Do not assume stability based on "no significant change" from prior ECG—clinical status and symptoms must guide management 1

Recommended Next Steps

Immediate Assessment:

• Evaluate vital signs, oxygen saturation, and clinical signs of hypoperfusion 1
• Assess for symptoms: chest pain, dyspnea, palpitations, lightheadedness, syncope 1
• Review for reversible causes of tachycardia as outlined above 1

If Symptomatic or Hemodynamically Unstable:

• Address the underlying cause (e.g., fluid resuscitation for dehydration, oxygen for hypoxemia) 1
• If cardiovascular compromise is directly related to the heart rate, consider synchronized cardioversion 1

If Asymptomatic with Stable Chronic Findings:

• Ensure optimal medical therapy for coronary artery disease and any underlying heart failure 1
• Consider echocardiography to definitively assess left atrial size, left ventricular hypertrophy, and ventricular function 3
• Obtain a repeat ECG at normal heart rate to clarify whether LVH voltage criteria persist 4