Clinical assessment and follow-up

Non-fasting blood samples to measure plasma L-arginine and ADMA concentrations were taken at the time of study enrollment (baseline value), in the morning before surgery (pre-operative value), and on days 1 and 3 after surgery. Safety parameters were assessed from the routine blood draws when the patient was entered into the study, on the morning before surgery, and at hospital discharge. All clinical evaluations and risk classifications (ASA score²² and RCRI²³) were performed in accordance with widely used protocols by trained anesthesiologists within the week preceding surgery. The RCRI accounts for ischemic heart disease, heart failure, diabetes, impaired renal function (serum creatinine >2 mg/dL or dialysis treatment), high-risk surgery, and history of cerebrovascular disease.

After surgery was complete, patients were monitored daily for the duration of their in-patient treatment, and all clinical events, changes in laboratory parameters, and clinical diagnostic tests that were scheduled based on routine clinical testing were documented. No additional clinical testing was performed.

After discharge, patients were followed-up by telephone using a structured questionnaire at day 30 after surgery; all serious adverse events occurring during that period were recorded and validated. The time course of the study is schematically represented in Figure 1.

Schematic representation of study timelines.

The primary end point was a composite end point that was defined by the occurrence of death (any cause), myocardial infarction or acute coronary syndrome, decompensated congestive heart failure, severe arrhythmia, major thrombosis, or embolism (cerebrovascular or pulmonary) from the beginning of surgery until 30 days after surgery.

Diagnosis of myocardial infarction was based on new persistent ST-segment (≥1 mm in ≥2 leads) or T-wave changes, new Q waves, and angiographic evidence or a positive troponin test. Acute coronary syndrome was defined as severe precordial chest pain lasting >30 minutes that was unresponsive to standard treatment and that was accompanied by ischemic electrocardiogram changes and identification of stenosis in coronary angiography, but that had negative cardiac enzymes and no development of Q waves. Diagnosis of decompensated congestive heart failure was based on dyspnea and rales indicative of pulmonary edema and confirmed by chest radiograph, and/or acute requirement of intravenous positive inotropic drugs or diuretics. Deep vein thrombosis was defined as loss of deep vein compressibility visualized by ultrasound. Pulmonary embolism suspected by shortness of breath in combination with jugular vein congestion and/or elevation of D-dimer >190 µg/L was to be confirmed by spiral computed tomography, magnetic resonance imaging, or ventilation perfusion scanning. Severe arrhythmia was defined as any of the following: primary cardiac arrest requiring resuscitation, atrial arrhythmia (e.g., atrial fibrillation or flutter requiring cardioversion or drug intervention for frequency control or stroke prevention), sustained or polymorphic ventricular tachycardia, or third-degree atrioventricular block.