What are the causes of low pressure severe tricuspid regurgitation?

Causes of Low Pressure Severe Tricuspid Regurgitation

Low pressure severe tricuspid regurgitation occurs when severe TR develops without significant pulmonary hypertension (typically RVSP <40-55 mmHg), and is most commonly caused by primary valve abnormalities, right ventricular dysfunction from intrinsic myocardial disease, or atrial fibrillation with annular dilatation rather than secondary to elevated pulmonary pressures.

Primary Valve Abnormalities (Structural Causes)

When severe TR occurs in the absence of elevated pulmonary pressures, primary tricuspid valve pathology should be suspected 1:

• Infective endocarditis - particularly in intravenous drug users, causing leaflet destruction without necessarily causing pulmonary hypertension 1
• Rheumatic valvulitis - though typically associated with left-sided disease, can cause isolated tricuspid pathology 1
• Carcinoid syndrome - causes valve thickening and retraction, often affecting both tricuspid and pulmonic valves 1
• Ebstein's anomaly - congenital apical displacement of the tricuspid valve 1
• Tricuspid valve prolapse - myxomatous degeneration causing leaflet prolapse 1
• Marfan syndrome - connective tissue disorder affecting valve structure 1
• Trauma - including iatrogenic injury from repeated endomyocardial biopsies or pacemaker lead placement 1
• Radiation therapy - causing valve fibrosis and dysfunction 1
• Rheumatoid arthritis - inflammatory valve involvement 1
• Anorectic drugs - medication-induced valvulopathy 1

Right Ventricular Dysfunction Without Pulmonary Hypertension

RV diastolic hypertension and cavity enlargement can cause severe functional TR even with normal pulmonary pressures 1:

• Dilated cardiomyopathy - RV dilatation causing annular dilatation and leaflet tethering without elevated PA pressures 1
• Right ventricular infarction - causing RV dysfunction and annular dilatation 1
• RV failure of any cause - leading to elevated RV diastolic pressures and annular dilatation 1

Atrial Fibrillation and Isolated Annular Dilatation

Chronic atrial fibrillation can cause progressive tricuspid annular dilatation leading to severe TR independent of pulmonary pressures 1:

• Atrial fibrillation is present in 70-88% of patients with severe TR and can be both cause and consequence 2
• Isolated annular dilatation without other cardiac pathology represents an increasingly recognized subgroup 3

Pacemaker-Related TR

Pacemaker leads can cause severe TR through mechanical interference with leaflet coaptation or direct leaflet injury 1:

• Lead-induced TR may be severe despite normal pulmonary pressures 1
• The technique for repair must be adapted when transvalvular leads are present 1

Key Clinical Distinction

The critical distinction in low-pressure severe TR is that pulmonary artery systolic pressures remain <55-60 mmHg 1:

• In acute pulmonary embolism, the RV can only generate PAsP up to 60 mmHg acutely, with tricuspid regurgitant jet velocities no higher than 2.5-3.5 m/s 1
• Conversely, PAsP >60 mmHg suggests chronic pulmonary hypertension or repeated embolic events 1
• Normal RVSP (e.g., 17 mmHg) with severe TR strongly suggests primary valve pathology or RV myocardial disease rather than pressure overload 4

Diagnostic Approach

When evaluating low-pressure severe TR, echocardiography should assess 1:

• Tricuspid valve structure and motion - to identify primary valve abnormalities
• Tricuspid annular size - dilatation suggests functional etiology
• RV size and function - cavity enlargement and systolic dysfunction
• Estimated pulmonary artery pressure - to confirm low-pressure state
• Presence of pacemaker leads - mechanical interference
• Left-sided valve function - to exclude secondary causes

Clinical Implications

Low-pressure severe TR carries different prognostic and therapeutic implications than high-pressure TR 5, 6:

• Five-year survival with severe TR and heart failure with reduced ejection fraction is only 34% 5
• Surgical mortality for isolated TR averages 8-10%, making patient selection critical 3
• Surgery should be considered before onset of irreversible RV dysfunction and end-organ damage in symptomatic patients at low operative risk 3
• The absence of pulmonary hypertension does not indicate benign disease - primary valve pathology may progress relentlessly 6, 3