A 48-year-old woman from Mumbai with a 10-year history of hypertension (BP 145/92 mmHg on amlodipine) and dyslipidaemia (LDL 145 mg/dL on atorvastatin 20 mg daily) attends a preventive cardiology clinic. She is asymptomatic with no prior cardiac events. To detect subclinical left ventricular dysfunction and guide intensification of therapy, which investigation is most appropriate?