How should I manage a patient with acute chest pain, new‑onset atrial fibrillation with a ventricular rate of 90 beats per minute and a blood pressure of 130/60 mm Hg?

Management of Chest Pain with New‑Onset Atrial Fibrillation

Immediate Assessment and Stabilization

Administer glyceryl trinitrate (GTN) for chest pain relief in this hemodynamically stable patient; GTN is safe at a blood pressure of 130/60 mm Hg and will not cause clinically significant hypotension. 1

• GTN primarily reduces systolic blood pressure rather than diastolic pressure, and the current BP of 130/60 provides adequate margin for safe administration. 2
• The 2002 European Heart Journal task force recommends short‑acting nitrates for suspected cardiac chest pain when there is no bradycardia or low blood pressure. 1
• Administer sublingual GTN 0.3–0.6 mg (or spray equivalent) and reassess chest pain after 3–5 minutes. 1

Concurrent Rate‑Control Strategy

Initiate intravenous diltiazem immediately for ventricular rate control while addressing the chest pain, as the ventricular rate of 90 bpm may be inadequate control in the setting of acute coronary syndrome. 1, 3, 4

Diltiazem Administration Protocol

• Give diltiazem 0.25 mg/kg IV (approximately 15–20 mg for a 70 kg patient) over 2 minutes as the initial bolus. 1, 3, 4
• If needed after 15 minutes, administer a second bolus of 0.35 mg/kg, followed by continuous infusion at 5–15 mg/h. 1, 3
• Onset of rate control occurs within 2–7 minutes, with maximal heart‑rate reduction typically achieved by 3 minutes. 4
• Target a lenient resting heart rate < 110 bpm initially; pursue stricter control (< 80 bpm) only if chest pain or other symptoms persist. 1, 3, 5

Why Diltiazem Over Beta‑Blockers in This Context

• In the setting of acute chest pain with new‑onset AF, diltiazem provides rapid rate control without the negative inotropic effects that may worsen cardiac output if acute coronary syndrome is present. 1, 3
• Beta‑blockers are equally effective for rate control but may be relatively contraindicated if the chest pain represents acute myocardial ischemia with borderline hemodynamics. 1, 3
• The FDA label for IV diltiazem specifically indicates its use for "temporary control of rapid ventricular rate in atrial fibrillation or atrial flutter." 4

Critical Safety Considerations

Do NOT use diltiazem if this patient has Wolff‑Parkinson‑White syndrome with pre‑excited atrial fibrillation, as AV‑nodal blocking agents can accelerate ventricular rate and precipitate ventricular fibrillation. 1, 3, 4

• The FDA label explicitly contraindicates diltiazem in "patients with atrial fibrillation or atrial flutter associated with an accessory bypass tract such as in Wolff‑Parkinson‑White (WPW) syndrome." 4
• If the ECG shows a wide QRS with delta waves suggesting pre‑excitation, proceed immediately to electrical cardioversion if unstable, or give IV procainamide if stable. 1, 3

Anticoagulation Initiation

Calculate the CHA₂DS₂‑VASc score immediately and initiate oral anticoagulation if the score is ≥2 (men) or ≥3 (women), regardless of whether the chest pain represents acute coronary syndrome. 1, 3, 5

• Direct oral anticoagulants (apixaban, rivaroxaban, edoxaban, dabigatran) are preferred over warfarin except in patients with mechanical heart valves or moderate‑to‑severe mitral stenosis. 1, 3, 5
• If warfarin is used, target INR 2.0–3.0 with weekly monitoring during initiation and monthly monitoring once stable. 1, 3

Diagnostic Work‑Up for Chest Pain

Obtain a 12‑lead ECG immediately to assess for ST‑segment elevation or depression, T‑wave inversion, or other signs of acute coronary syndrome, and measure high‑sensitivity troponin. 1, 6, 7

• The 2002 European Heart Journal guideline emphasizes that "severe prolonged chest pain of acute onset" calls for immediate hospital care and evaluation for myocardial infarction, unstable angina, aortic dissection, or pulmonary embolism. 1
• Troponin elevation can assist in determining the risk of adverse outcomes, but universal troponin testing is not required in low‑risk patients with recurrent paroxysmal AF similar to prior episodes. 6
• Obtain a transthoracic echocardiogram to assess left‑ventricular function, left‑atrial size, valvular disease, and structural abnormalities. 3, 5, 7

Rhythm‑Control Considerations

Do NOT attempt immediate cardioversion in this hemodynamically stable patient with new‑onset AF of unknown duration, as the risk of thrombo‑embolism is substantial without adequate anticoagulation. 1, 3

• For AF lasting > 48 hours or of unknown duration, provide therapeutic anticoagulation for at least 3 weeks before elective cardioversion and continue for a minimum of 4 weeks afterward. 1, 3
• Alternatively, perform transesophageal echocardiography to exclude left‑atrial thrombus; if negative, proceed with cardioversion after initiating heparin. 1, 3
• Immediate electrical cardioversion is reserved for hemodynamically unstable patients (e.g., symptomatic hypotension with systolic BP < 90 mm Hg, acute pulmonary edema, ongoing refractory chest pain, altered mental status, or shock). 1, 3

Monitoring and Disposition

Admit this patient for continuous cardiac monitoring, serial troponins, and observation for at least 24 hours given the combination of chest pain and new‑onset AF. 1, 6

• Continuous ECG monitoring and frequent blood pressure measurement are required during IV diltiazem infusion. 4
• A defibrillator and emergency equipment should be readily available. 4
• If hypotension occurs during diltiazem administration, it is generally short‑lived but may last 1–3 hours; 3.2% of patients require intervention (IV fluids or Trendelenburg position) for blood pressure support. 4

Common Pitfalls to Avoid

• Do not withhold GTN solely because of the presence of atrial fibrillation; the blood pressure of 130/60 provides adequate margin for safe nitrate administration. 1, 2
• Do not rely on digoxin as the sole rate‑control agent in new‑onset AF, as it is ineffective during sympathetic surges and takes hours to achieve therapeutic effect. 1, 3, 5
• Do not discontinue anticoagulation if sinus rhythm is restored; stroke risk is determined by the CHA₂DS₂‑VASc score, not by rhythm status. 1, 3
• Do not combine beta‑blockers with diltiazem except under specialist supervision, as the risk of severe bradycardia and heart block is substantial. 1, 3