Tricuspid Valve Disease Pathophysiology

Introduction

The tricuspid valve is the largest of the four cardiac valves, located between the right atrium (RA) and right ventricle (RV). Despite its anatomical significance, tricuspid valve disease (TVD) has historically received less attention compared to left-sided valvular pathologies, such as mitral or aortic valve disease. However, with advances in echocardiography and increased awareness, the importance of tricuspid pathology is being increasingly recognized.

Tricuspid valve disease includes both tricuspid stenosis (TS) and tricuspid regurgitation (TR), which can occur independently or in combination. Unlike left-sided lesions that primarily cause pulmonary congestion and systemic hypoperfusion, right-sided valve diseases manifest predominantly with systemic venous congestion.

This article provides a detailed overview of the mechanisms, causes, clinical picture, and diagnostic challenges of tricuspid valve disease.

1. Anatomy and Physiology of the Tricuspid Valve

The tricuspid valve consists of:

Leaflets (cusps): anterior, posterior, and septal.
Chordae tendineae attaching the cusps to papillary muscles.
Annulus: a fibrous ring supporting the valve.

Function

Opens during diastole → allows systemic venous return from RA to RV.
Closes during systole → prevents retrograde flow into RA.

Unlike left-sided valves, the tricuspid valve operates under low pressure gradients, which influences both the pathophysiology and clinical consequences of its dysfunction.

2. Tricuspid Stenosis vs Tricuspid Regurgitation

A. Tricuspid Stenosis (TS)

Definition: Narrowing of the tricuspid orifice → impaired RA emptying into RV.

Hemodynamics:

Increased RA pressure.
RA enlargement and systemic venous hypertension.
Reduced RV filling → diminished cardiac output.

Pathophysiology:

Because the right heart is low-pressure, stenosis must be severe before symptoms appear.
Often coexists with mitral stenosis (rheumatic disease).

B. Tricuspid Regurgitation (TR)

Definition: Incomplete closure of the valve → systolic backflow from RV to RA.

Types:

Primary TR (organic): due to intrinsic valve leaflet pathology.
Secondary TR (functional): due to RV dilation or pulmonary hypertension, with normal valve leaflets.

Hemodynamics:

RV volume overload.
RA dilation and systemic venous congestion.
In severe TR, forward cardiac output falls significantly.

Pathophysiology:

TR is more common than TS.
Frequently secondary to left-sided heart disease or pulmonary hypertension.

3. Causes of Tricuspid Valve Disease

A. Rheumatic Heart Disease

Major cause of tricuspid stenosis worldwide.
Usually associated with mitral and aortic lesions.
Leads to leaflet thickening, commissural fusion, and calcification.

B. Pulmonary Hypertension

Secondary TR is common in patients with chronic left-sided heart failure, mitral stenosis, or chronic lung disease.
Elevated pulmonary pressures → RV dilation and annular dilation → TR.

C. Carcinoid Syndrome

Neuroendocrine tumors secrete serotonin and vasoactive substances.
Cause fibrous plaques on right-sided valves, particularly the tricuspid and pulmonic.
Leads to TR and, less commonly, TS.

D. Infective Endocarditis

Especially in IV drug users, where the tricuspid valve is the most commonly affected.
Valve destruction → severe TR.

E. Congenital Causes

Ebstein’s anomaly: malformation of the tricuspid valve, leading to displacement and regurgitation.
Other congenital malformations may also cause dysfunction.

F. Iatrogenic and Device-Related

Pacemaker or ICD leads can interfere with valve closure, leading to TR.
Post-surgical trauma may also contribute.

4. Clinical Manifestations

A. Symptoms of Tricuspid Stenosis

Fatigue (low cardiac output).
Abdominal discomfort (congestive hepatomegaly).
Peripheral edema.
Ascites and anasarca in advanced disease.

B. Symptoms of Tricuspid Regurgitation

Fatigue and weakness due to reduced forward output.
Systemic venous congestion:
- Peripheral edema.
- Ascites.
- Hepatic congestion → pulsatile hepatomegaly.
- Anorexia, early satiety (congestive hepatopathy).
Jugular venous distension with prominent v waves.

C. Physical Signs

In TS:

Elevated jugular venous pressure (JVP) with giant a waves.
Diastolic rumble at left lower sternal border, increasing with inspiration.

In TR:

Elevated JVP with prominent cv waves and systolic pulsations.
Pulsatile liver (systolic expansion).
Holosystolic murmur at left lower sternal border, augmented with inspiration (Carvallo’s sign).
Peripheral edema, ascites.

5. Diagnostic Challenges

Diagnosing tricuspid valve disease is often more complex compared to left-sided lesions.

A. Overlapping Symptoms

Symptoms of TVD often mimic advanced left-sided heart disease or pulmonary hypertension.
Edema and ascites may be misattributed to hepatic or renal disease.

B. Auscultation Challenges

Tricuspid murmurs are low-pitched and may be drowned out by left-sided murmurs.
Carvallo’s sign (inspiratory augmentation of TR murmur) helps distinguish TR from mitral regurgitation.

C. Imaging Modalities

Echocardiography (first-line):
- TS: thickened leaflets, restricted motion, elevated diastolic gradient.
- TR: annular dilation, regurgitant jet on Doppler, hepatic vein systolic flow reversal (severe TR).
- Assessment of RV size and function.
Doppler Echocardiography:
- Quantifies regurgitant flow.
- Helps estimate pulmonary pressures.
Cardiac MRI:
- Provides accurate RV volumes and regurgitant fractions.
- Useful in congenital anomalies and complex cases.
Catheterization:
- Hemodynamic assessment in difficult cases.
- Measures RA pressure, RV pressure, and transvalvular gradients.

D. Confounding Factors

TR may be secondary, so addressing pulmonary hypertension or left-sided lesions can improve valve competence.
TS is often masked by coexisting mitral stenosis.

6. Clinical Course and Complications

Tricuspid stenosis: Progressive RA enlargement, atrial fibrillation, systemic venous congestion.
Tricuspid regurgitation: RV dilation and dysfunction, severe right-sided heart failure.
Both conditions predispose to arrhythmias and thromboembolic complications.