Review Question - QID 109550

A 68-year-old man presents to the emergency department with chest pain and shortness of breath. These symptoms have been worsening over the past year and are now restricting him from his activities of daily living. The patient has a past medical history of obesity, diabetes, constipation, dyslipidemia, and hypertension. His current medications include aspirin, atorvastatin, insulin, metformin, and lisinopril. His temperature is 99.5°F (37.5°C), blood pressure is 160/95 mmHg, pulse is 90/min, respirations are 15/min, and oxygen saturation is 98% on room air. On physical exam, you note a man who is uncomfortable. His cardiac exam is notable for jugular venous distension and an early heart sound after S2. A pulmonary exam is notable for bibasilar crackles. An ECG is performed as seen in Figure A. Laboratory values are ordered as seen below.

Hemoglobin: 13 g/dL
Hematocrit: 39%
Leukocyte count: 7,500 cells/mm^3 with normal differential
Platelet count: 177,000/mm^3

Serum:
Na+: 139 mEq/L
Cl-: 100 mEq/L
K+: 4.3 mEq/L
HCO3-: 25 mEq/L
BUN: 29 mg/dL
Glucose: 169 mg/dL
Creatinine: 1.5 mg/dL
Ca2+: 10.2 mg/dL
AST: 12 U/L
ALT: 20 U/L

Which of the following is the most important risk factor for this patient's condition?