Table 3.

List of investigations and their implications

Parameter	Implications
Blood Hemoglobin	Anemia is common because of dietary restrictions. Also possible in case of severe paravalvular leak
Platelet count	As they are often on anti-platelet agents. Also, patient receiving UFH/LMWH for more than 4 days are susceptible to develop heparin induced thrombocytopenia
Reticulocyte count	Rises along with serum LDH because of paravalvular or transvalvular leak. In cases of sub clinical hemolysis, haptoglobin level might be low
Liver Function Tests	Features of intravascular hemolysis like raised indirect bilirubin, raised serum lactate dehydrogenase (LDH) and mildly raised serum aspartate transaminase (AST), suggest paravalvular or transvalvular (due to pannus ingrowth or thrombus formation on the mechanical valve) leak
Prothrombin time (PT) and international normalized ratio (INR)	To confirm adequacy of anticoagulation VKA therapy.
Activated partial thromboplastin time (APTT)	To confirm adequacy of anticoagulation if the patient is on UFH
Kidney Function Test	Might be deranged in case of valve dysfunction (low cardiac output state), choice of bridging therapy will depend upon presence of renal dysfunction.
Serum electrolytes (sodium & potassium)	Patients are usually on a salt restricted diet and diuretic, and so might have sub clinical hyponatremia. They are also commonly on ACE inhibitors or ARBs, which can cause hyperkalemia
Posteroanterior view of chest skiagram	To look for evidence of pulmonary hypertension, as they are more prone to develop pulmonary edema, atelectasis and pulmonary complications.
Transthoracic Echocardiography	Function of valve (movement of leaflets, pressure gradient across the implanted prosthetic valve, determination of effective valvular area, para-valvular leak, any vegetation),  Regional and global left and right ventricular systolic function and size,  Atrial size, enlarged LA with auto contrast,  Function of native valves (Other than the one (s) replaced)  Estimate of pulmonary artery pressure.
Transesophageal Echocardiography	Assessment of LV function in case of Mitral valve prosthesis  For assessment of posterior aspect of aortic valve and is sensitive in detection of vegetation and abscess formation  Provides superior imaging of LA side of mitral valve prosthesis

UFH-Unfractionated heparin, LMWH: Low molecular weight heparin, VKA: Vitamin K antagonist, ACE: Angiotensin converting enzyme inhibitor, ARB: Angiotensin II receptor blockers, LA: Left atrium, LV: Left ventricle