P. 337

are also other indicators of PH in dogs with MMVD. A study suggested that a tricuspid pressure gradient was associated with a combination of either an increased or decreased left ventricular diastolic dimension, decreased pulmonary arterial acceleration/deceleration time, increased right ventricular diastolic diameter and left atrial to aortic root (LA/Ao) ratio.
Treatment of PH
Because most cases of PH are secondary to an underlying disease process, treatment aimed at eliminating or improving the underlying disease status is the basis for therapy. If the PH is not controlled by primary disease therapy or if the etiology of the PH appears to be idiopathic, then direct pulmonary arterial pressure modulation through the use of pulmonary vasodilators should be implemented. For example, it is
An Urban Experience
not uncommon that MMVD dogs with a recent onset
of signs of CHF present with mild PH that may reverse once effective CHF therapy has started. Dogs with PH despite having their signs of CHF controlled by medical therapy probably bene t from medical therapy aimed
at reducing pulmonary arterial pressure, but there are few veterinary studies available supporting this. Dogs with more pronounced PH are more likely to bene t from this type of therapy. In human medicine, there
are several different medical treatments available,
such as endothelin-receptor blockers, prostacyclin analogues, and L-arginine, but these are not available
in veterinary patients because of costs and lack of ef cacy in this specie. The current most commonly used drug for controlling PH in dogs is, therefore, Sildena l. Pimobendan is another drug that lowers the pulmonary arterial pressure (as well as systemic arterial resistance).
Pulmonary arterial hypertension
Secondary to other disease
Collagen vascular disease
Congenital left-to-right shunt
Portal hypertension
HIV infection
Drugs and toxins
Other conditions
Associated with substantial venous or capillary involvement
Pulmonary veno-occlusive disease
Pulmonary capillary hemangiomatosis
Persistent pulmonary hypertension of newborn
Pulmonary hypertension with left heart disease
Left-sided atrial or ventricular disease
Left-sided valvular heart disease
Pulmonaty hypertension associated with lung disease
Chronic obstructive pulmonary disease
Interstitial lung disease
Upper airway obstruction
Alveolar hypoventilation disorders
Exposure to high altitude
Developmental abnormalities
Pulmonary hypertension due to chronic thrombotic or embolic disease or both
Thromboembolic obstruction of proximal pulmonary arteries
Thromboembolic obstruction of distal pulmonary arteries
Nonthrombotic pulmonary embolism (tumuor, parasites, foreign body)
Pulmonary Langerhans’ cell histiocytosis
Compression of pulmonary vessels
Fibrosing mediastinitis
Table 1. Pulmonary Hypertension World Health Organisation (WHO) clinical classi cation system based on etiology

   335   336   337   338   339