The tricuspid valve has three leaflets: the anterior, posterior and medial or septal leaflets. Together, these separate the right atrium from the right ventricle. During systole, or muscle contraction, the tricuspid valve closes, and during diastole, or heart relaxation, the tricuspid valve opens and lets blood fill the right ventricle. Tricuspid valve regurgitation happens when the tricuspid valve doesn’t close completely and blood leaks back from the right ventricle into the right atrium. Tricuspid valve stenosis happens if the tricuspid valve can’t open completely, making it difficult to fill the right ventricle.
Let’s start with tricuspid valve regurgitation. Often, regurgitation is due to pulmonary hypertension which causes an increase in right ventricular pressure. This pressure then dilates the tricuspid valve, allowing blood to go backward. Another well-known cause of regurgitation is rheumatic heart disease, an autoimmune reaction that involves the valve leaflets and causes inflammation. This chronic inflammation leads to leaflet fibrosis, which makes it so that they don’t form a nice seal and instead let blood leak through. Still another cause of tricuspid regurgitation is damage to the papillary muscles from a heart attack. If these papillary muscles die, they can’t anchor the chordae tendineae, which then allows the tricuspid valve to flop back and allows blood to flow backward from the right ventricle into the right atrium. There are also congenital causes for this condition, like Ebstein’s anomaly, which is when a person is born with leaflets that are located too low, i.e., in the ventricle rather than between the atria and the ventricle, and this makes it hard for the leaflets to form a nice seal.
In all of these situations, blood flows back into the right atrium during systole. This movement of blood can be heard as a holosystolic murmur, because it’s possible to hear blood flowing through the valve for the duration of systole. Another possible effect is Carvallo’s sign, which is when the murmur gets louder with inspiration, or inhalation. This happens because the negative pressure in the chest brings more blood back up into the heart, and more blood makes the murmur even noisier.
Now, that extra blood that flowed backward into the atrium during systole ends up draining right back into the ventricle during diastole. This mean’s there’s an increase in right ventricular preload. It’s kind of like if you were digging a hole and every time you shoveled some dirt out, half of it fell back in; that’s a lot of wasted work.
Eventually, to deal with this extra blood and the extra work required to pump it out, the right ventricle grows larger, a process called eccentric ventricular hypertrophy. In this situation, new sarcomeres are added in series to existing ones. This remodeling, or structural change, in the heart stretches the annulus, or ring of the valve, letting more blood leak back into the atrium and actually therefore worsening the regurgitation.
