Left Atrial Enlargement and Pulmonary Hypertension

Primary Pathophysiological Mechanisms

The American College of Cardiology notes that hypertension is the most common cause of left ventricular diastolic dysfunction, producing left ventricular hypertrophy and impaired relaxation that elevates left-sided filling pressures even when systolic function appears normal 1
The European Society of Cardiology states that up to 60-70% of patients with isolated diastolic dysfunction develop pulmonary hypertension 1
Mitral regurgitation causes both volume overload of the left atrium and elevated left atrial pressure, according to the American College of Cardiology 2
Mitral stenosis produces left atrial enlargement with relatively preserved left ventricular size, but high transmitral gradients, as noted by the American College of Cardiology 2
Mixed mitral disease (stenosis plus regurgitation) causes left ventricular remodeling in addition to left atrial enlargement, with pathological consequences incremental to either lesion alone, according to the American College of Cardiology 2

The European Respiratory Society notes that two distinct subtypes exist within PH-LHD: isolated post-capillary PH (Ipc-PH) and combined post- and pre-capillary PH (Cpc-PH) 3
Isolated post-capillary PH (Ipc-PH) is characterized by pulmonary capillary wedge pressure >15 mm Hg without intrinsic pulmonary vascular disease, normal pulmonary vascular resistance, as defined by the European Respiratory Society 3
Combined post- and pre-capillary PH (Cpc-PH) is characterized by persistent elevation in left atrial pressure triggering secondary pulmonary vascular remodeling, vasoconstriction, and increased pulmonary vascular resistance, according to the European Respiratory Society 3

The American College of Cardiology recommends comprehensive Doppler echocardiography as the primary screening tool to evaluate left ventricular systolic and diastolic function, valvular morphology and function, left atrial size, and estimated pulmonary artery systolic pressure 1
The European Society of Cardiology states that right heart catheterization is indicated when pulmonary hypertension appears severe or disproportionate to the degree of left heart disease, or when diagnostic uncertainty exists between pulmonary arterial hypertension and PH-LHD 3
The European Respiratory Society notes that hemodynamic confirmation requires pulmonary capillary wedge pressure >15 mm Hg 3

The European Society of Cardiology recommends optimizing underlying left heart disease as the primary therapeutic goal, including aggressive treatment of hypertension, diastolic dysfunction, and valvular disease 3
The American College of Cardiology states that diuretics should be used aggressively to reduce left-sided filling pressures and pulmonary congestion, and that ACE inhibitors or ARBs should be used for afterload reduction and to prevent/reverse left ventricular hypertrophy 1
The European Respiratory Society notes that PAH-specific therapies are not recommended in PH-LHD, as they can cause harm, and that this is a Class III recommendation indicating harm 3

The American College of Cardiology warns that misdiagnosing PH-LHD as pulmonary arterial hypertension is the most critical error, leading to inappropriate PAH-specific therapy that causes patient harm, and recommends systematically evaluating for left heart disease risk factors and carefully assessing echocardiographic features of left ventricular dysfunction and left atrial enlargement 1
The European Respiratory Society notes that assessing hemodynamics before optimizing volume status can lead to incorrect diagnosis, and recommends always optimizing diuretic therapy before invasive assessment 3