The classification continues to evolve based on improved understanding of the disease mechanisms.Most recently in 2015, the WHO guidelines were updated by the European Society of Cardiology (ESC) and European Respiratory Society (ERS). These guidelines are endorsed by the International Society for Heart and Lung Transplantation, and provide the current framework for understanding and treatment of pulmonary hypertension. Genetics
Mutations in several genes have been associated with this condition these include bone morphogenetic protein receptor type 2 (BMPR2) and eukaryotic translation initiation factor 2 alpha kinase 4 gene (EIF2AK4). Pathogenesis
The pathogenesis of pulmonary arterial hypertension (WHO Group I) involves the narrowing of blood vessels connected to and within the lungs. This makes it harder for the heart to pump blood through the lungs, as it is much harder to make water flow through a narrow pipe as opposed to a wide one. Over time, the affected blood vessels become stiffer and thicker, in a process known as fibrosis. The mechanisms involved in this narrowing process include vasoconstriction, thrombosis, and vascular remodeling (excessive cellular proliferation, fibrosis, and reduced apoptosis/programmed cell death in the vessel walls, caused by inflammation, disordered metabolism and dysregulation of certain growth factors). This further increases the blood pressure within the lungs and impairs their blood flow. In common with other types of pulmonary hypertension, these changes result in an increased workload for the right side of the heart. The right ventricle is normally part of a low pressure system, with systolic ventricular pressures that are lower than those that the left ventricle normally encounters.
Or, those impulses can be merged with complexes that are originated in the ventricle and produce a summation pattern (fusion complexes).Less common is ventricular tachycardia that occurs in individuals with structurally normal hearts. This is known as idiopathic ventricular tachycardia and in the monomorphic form coincides with little or no increased risk of sudden cardiac death. In general, idiopathic ventricular tachycardia occurs in younger individuals diagnosed with VT. While the causes of idiopathic VT are not known, in general it is presumed to be congenital, and can be brought on by any number of diverse factors. Treatment
Therapy may be directed either at terminating an episode of the abnormal heart rhythm or at reducing the risk of another VT episode. The treatment for stable VT is tailored to the specific person, with regard to how well the individual tolerates episodes of ventricular tachycardia, how frequently episodes occur, their comorbidities, and their wishes. Individuals with pulseless VT or unstable VT are hemodynamically compromised and require immediate electric cardioversion to shock them out of the VT rhythm. Cardioversion
If a person still has a pulse, it is usually possible to terminate the episode using electric cardioversion. This should be synchronized to the heartbeat if the waveform is monomorphic if possible, in order to avoid degeneration of the rhythm to ventricular fibrillation. An initial energy of 100J is recommended. If the waveform is polymorphic, then higher energies and an unsynchronized shock should be provided (also known as defibrillation).