Echocardiographic changes induced by moderate to marked hypobaric hypoxia in dogs

Abstract

Hypobaric (high-altitude) hypoxia is a physiologic cause of pulmonary hypertension, and alters left ventricular (LV) systolic and diastolic function. In the presence of tricuspid regurgitation, systolic pulmonary artery pressure can be measured noninvasively using the peak tricuspid regurgitation velocity and the Bernoulli equation. In the absence of measurable tricuspid regurgitation, severity of pulmonary hypertension may be estimated using two-dimensional, M-mode, and Doppler-derived parameters. To evaluate the usefulness of echocardiographic parameters for detecting mild-to-moderate pulmonary hypertension caused by moderate-to-marked hypoxia and to study the effect of high-altitude hypoxia on systolic and diastolic LV function in dogs, 19 Greenland dogs were examined at moderate altitude (2300 m) and high altitude (3500 m), and 10 Greenland control dogs were examined at 700-900 m. Evaluated parameters were pulmonary flow profile (shape, right ventricular acceleration time (RVAT), ejection time (RVET), RVAT/ET), peak mitral inflow velocities (LVE, LVA, LVE/A-ratio), LV % fractional shortening (FS), systolic time intervals (LVPEP, LVPEP/ET), and stroke volume index (SVI). Notching during deceleration was common in dogs at high altitude and in the control dogs, but not in dogs at moderate altitude. RVAT was shorter in dogs at high altitude compared with moderate altitude, but not compared with control dogs. Peak A-velocity was higher and E/A-ratio was lower in dogs at high altitude compared with moderate altitude and control dogs. FS was increased in dogs at high altitude compared with moderate altitude, and LVPEP and LVPEP/ET were shorter in the dogs at high altitude compared with moderate altitude and control dogs. In conclusion, significant differences in pulmonary flow profiles and systolic and diastolic parameters can be observed echocardiographically in dogs at different degrees of hypobaric hypoxia. However, overlap between the groups compromises their usefulness for diagnosing and estimating the degree of mild-to-moderate pulmonary hypertension in individual dogs.

Diagnostic Value of Echo-Doppler and Tissue Doppler Imaging in Dogs with Pulmonary Arterial Hypertension

“…[1][2][3] Recognition of the prevalence and clinical importance of PAH associated with cardiovascular and respiratory diseases in dogs is increasing because of the current wide use of Doppler echocardiography. [2][3][4][5] Doppler assessment of tricuspid valve regurgitation (TR) or pulmonic valve regurgitation (PR) can be used to indirectly assess SPAP and diastolic PAP, respectively. These noninvasive estimates of PAP have been demonstrated to be strongly correlated with invasively measured PAP values in humans.…”

“…The SPAP usually ranges from 15 to 25 mm Hg in healthy dogs. 1 However, SPAP increases under several physiologic conditions, including altitude or athletic status, 1,5 and the threshold of SPAP values assessed by the Doppler technique to define PAH varies from 31 to 45 mm Hg. [2][3][4] Moreover, although TR and PR have been described as commonly found by colorDoppler mode in healthy dogs, a,10,11 such regurgitation can be absent or inadequate for PAP quantification, thus precluding confirmation of PAH.…”

“…[2][3][4] Moreover, although TR and PR have been described as commonly found by colorDoppler mode in healthy dogs, a,10,11 such regurgitation can be absent or inadequate for PAP quantification, thus precluding confirmation of PAH. 5 In such dogs, several indirect markers of PAH have been proposed, including biochemical variables 12 or echocardiographic alterations, such as right ventricular (RV) remodeling and flattening or paradoxical movement of the interventricular septum. However, these latter findings usually occur in moderate-to-severe PAH and thus are of limited diagnostic value.…”

“…4 However, AT and AT/ET are not useful for diagnosing and estimating mild-to-moderate PAH induced by altitude. 5 Several other Doppler markers have been proposed for the noninvasive detection of PAH. As an example, the interest of the Tei index (TEI), a marker of global myocardial performance, has been demonstrated for the diagnosis and therapeutic follow-up of PAH in man and sheep.…”

Echocardiographic assessment of right heart indices in dogs with elevated pulmonary artery pressure associated with chronic respiratory disorders, heartworm disease, and chronic degenerative mitral valvular disease

“…Primary pulmonary artery hypertension in dogs has rarely been studied. Common secondary causes of PH in dogs include left-sided heart failure, increased pulmonary blood flow, increased pulmonary vascular resistance caused by conditions such as obstructive pulmonary vascular disease, thromboembolic disease, pulmonary parenchymal disease, and chronic hypoxia (Glaus et al 2004;Schober and Baade 2006;Serres et al 2006). CDMD can lead to left heart dilation and increased left atrial pressure, causing elevated pulmonary venous pressure (post-capillary PH), pulmonary oedema and chronic post-capillary hypoxia.…”