To likely compensate for the cells energy demand, an upregulation of fatty acid β-oxidation and a decreased concentration of certain amino acids that feed anaplerotically into the citrate cycle, such as glutamine (via the fifth site of the citrate cycle), leucine, isoleucine, threonine (all via the sixth site of the citrate cycle) and aspartate (via the 10th site of the citrate cycle), could be detected. In summary, this reduced mitochondrial respiration and glycolytic flux results in impaired mitochondrial flexibility with a large dependence on fatty acid β-oxidation.However, neurons, with the exception of hypothalamic neurons, are not capable of satisfying their large energy demands by degrading fatty acids. It is speculated that an upregulation of β-oxidation also occurs in brain cells due to the hypofunctional mtFASII pathway. The consequence would be an increased risk for hypoxia and oxidative stress, which may contribute to neurological symptoms in the long term. Methylmalonic acid
Methylmalonic acid is formed from the essential amino acids valine, methionine, threonine and isoleucine, from odd-chained fatty acids, from propionate and from cholesterol side chain, on the degradation path into the citrate cycle. In this process, the last intermediate methylmalony-CoA can be converted to methymalonic acid by a deacylase before incorporation at the succinyl-CoA site of the citrate cycle. At this point, the acyl-CoA synthease encoded by ACSF3 could convert the methylmalonic acid back to methylmalonyl-CoA and then feed it to the citrate cycle with the help of the methylmalonyl-CoA mutase and its cofactor vitamin B12.
However, the murmur may be inaudible due to the  relatively low pressures in the right side of the heart. A third heart sound may also be present, also heard at the lower sternal border, and increasing in intensity with inspiration.On examination of the neck, there may be giant C-V waves in the jugular pulse. With severe TR, there may be an enlarged liver detected on palpation of the right upper quadrant of the abdomen; the liver may be pulsatile on palpation and even on inspection. Causes
The causes of TR may be classified as  congenital or acquired; another classification divides the causes into primary or secondary. Congenital abnormalities are much less common than acquired. The most common acquired TR is due to right ventricular dilatation. Such dilatation is most often due left heart failure or pulmonary hypertension. Other causes of right ventricular dilatation include right ventricular infarction, inferior myocardial infarction, and cor pulmonale.In regards to primary and secondary causes they are:

Mechanism
In terms of the mechanism of tricuspid insufficiency, it involves the expansion of the tricuspid annulus (fibrous rings of heart). Tricuspid insufficiency is linked to geometric changes of the tricuspid annulus (decreased tricuspid annular release). The leaflets shape are normal but prevented from normal working mechanism due to a distortion of spatial relationships of leaflets and chords. It is also contemplated that the process via which tricuspid regurgitation emerges, is a decrease of contraction of the myocardium around the annulus. Diagnosis
The diagnosis of TR may be suspected if the typical murmur of TR is heard.