Page 336 - WSAVA2017
P. 336

An Urban Experience
WSVA7-0378
CARDIOLOGY II
DIAGNOSIS AND MANAGEMENT OF PULMONARY HYPERTENSION IN DOGS
H. Jens1
1Uppsala, Sweden
DIAGNOSIS AND MANAGEMENT OF PULMONARY HYPERTENSION IN DOGS
Jens Häggström
Professor, DVM, PhD, DECVIM-CA (Cardiology)
Professor of Internal Medicine
Department of Clinical Sciences, Faculty of Veterinary Medicine and Animal Science
Swedish University of Agricultural Sciences, Uppsala, Sweden
Jens.Haggstrom@slu.se
Introduction
Pulmonary hypertension (PH) is defined as a pulmonary arterial systolic pressure >30 mmHg. Right-heart catheterization is considered the “gold standard” for diagnosis of PH. PH is a complex syndrome that has historically resulted in a poor prognosis. Pulmonary arterial pressure (PAP) is influenced by pulmonary blood flow, pulmonary vascular resistance (PVR), and pulmonary venous pressure. The elevated PAP of the syndrome of PH may be caused by pulmonary vascular abnormalities associated with increased blood flow
(i.e, “hyperkinetic” PH secondary to a patent ductus arteriosus), changes affecting resistance to flow (precapillary pulmonary arterial hypertension, PAH)
or caused by increased “downstream” resistance (postcapillary pulmonary venous hypertension, PVH). Diagnosis of PH requires diagnostic testing that quantifies the degree of elevation of PAP, determines
the underlying disease process if possible, and identifies the degree of hemodynamic impairment. Significant advances in therapy that target the derangements of the PH pathophysiology have been made in animals and people, providing an improved prognosis for survival and better quality of life in dogs. This presentation will review the most common diagnoses associated with PH and how PH may be managed.
Classification of PH
Pulmonary hypertension can be classified as pre- or postcapillary PH, or can be classified based on the disease process causing PH. The categories include pulmonary arterial hypertension, pulmonary venous hypertension, hypoxic PH, PH secondary to respiratory disease, PH secondary to thromboembolic disease,
and PH secondary to miscellaneous etiologies (Table 1). Geriatric dogs are likely to develop pulmonary fibrosis, but the most common cause for PH in dogs, by far, is left sided valvular heart disease, i.e. myxomatous mitral valve disease (MMVD) accounting for 40-85% of the cases.
PH in MMVD
The mitral regurgitation (MR) leads to increased pulmonary venous pressure. The processes that
govern the development of PH in MR are multifactorial and are not yet fully understood. Elevation of left atrial pressure, which occurs not only in acute MR, but also
in chronic MR, is believed to be the initiating factor in the pathogenesis of PH. Sustained elevation of left
atrial pressure, which is passively transmitted backward into the pulmonary veins, can lead to disruption of the delicate alveolar-capillary complex in a process known as alveolar capillary stress failure, with resulting capillary leakage and pulmonary edema. In the initial phases, this lesion may be reversible. However, with long-standing pulmonary venous hypertension, the alveolar-capillary unit may be irreversibly altered by a remodeling process characterized by excessive type IV collagen deposition, leading to a reduction in alveolar diffusion capacity.
The result is an increased resistance of the pulmonary arteries, and increased pressure in the pulmonary artery. The right ventricle has limited capacity of compensating for an increased pulmonary arterial pressure and usually dilate in response. Dogs with MMVD should always
be thoroughly examined by echocardiography for the presence of tricuspid regurgitation.
Diagnosis of PH
In veterinary medicine, right-heart catheterization is rarely performed in routine practice, and echocardiography
is the standard noninvasive technique for the diagnosis of PH. The maximal flow of this regurgitation is useful
in assessing the severity of PH, because the right ventricular pressure may be estimated using the modified Bernouilli equation (which gives an estimate of the tricuspid pressure gradient). Adding estimated right
atrial pressure to this pressure gradient may provide
an estimate of the right ventricular systolic pressure. A right ventricular systolic pressure of 30-45 mmHg has been suggested to be the cutoff for diagnosing PH in dogs, and a study showed that a tricuspid pressure gradient of >55 mmHg confers a worse outcome. There
  336
 42ND WORLD SMALL ANIMAL VETERINARY ASSOCIATION CONGRESS AND FECAVA 23RD EUROCONGRESS
  






























































   334   335   336   337   338