Soru

During a weekend visit with her family, a 62-year-old woman experiences progressively worsening shortness of breath and a 'racing heart' over a 48-hour period. She is evaluated in the acute care clinic, where she frantically states, 'I feel like I am having a severe panic attack; I just cannot catch my breath.' The patient's medical history includes chronic obstructive pulmonary disease (COPD), bipolar disorder (for which she currently takes no medications), and hypothyroidism (managed with levothyroxine). Her most recent echocardiogram from three months prior showed normal left ventricular systolic function with an ejection fraction of $60\%$.

Vital signs are temperature $37.2^{\circ}\text{C}$ ($99.0^{\circ}\text{F}$), blood pressure $136/84 \text{ mmHg}$, pulse $152\text{/min}$, and respirations $26\text{/min}$. Pulse oximetry shows $91\%$ on room air.

Physical examination reveals an irregularly irregular pulse. Lung auscultation demonstrates bilateral basilar crackles and diffuse expiratory wheezes. Trace bilateral lower extremity edema is present.

An electrocardiogram (ECG) reveals an irregularly irregular rhythm with absent P waves, narrow QRS complexes, and a ventricular rate of $152\text{/min}$.

Laboratory testing shows:
- Brain natriuretic peptide (BNP): $720 \text{ pg/mL}$ (Normal: $<100 \text{ pg/mL}$)
- Thyroid-stimulating hormone (TSH): $0.2 \mu\text{U/mL}$ (Normal: $0.4-4.0 \mu\text{U/mL}$)
- Free $T_4$: $0.7 \text{ ng/dL}$ (Normal: $0.8-1.8 \text{ ng/dL}$)

Arterial blood gas on room air reveals:
- $pH = 7.52$
- $pCO_2 = 26 \text{ mmHg}$
- $pO_2 = 62 \text{ mmHg}$
- $HCO_3^- = 20 \text{ mEq/L}$

Which of the following is the most appropriate next step in management?