Contrasting Effects of Inhibition of Phosphodiesterase 3 and 5 on Cardiac Function and Interstitial Fibrosis in Rats With Isoproterenol-Induced Cardiac Dysfunction.

Myocardial relaxation and stiffness are influenced by fibrillar collagen content. Cyclic nucleotide signaling regulators have been investigated targeting more effective modulation of collagen deposition during myocardial healing process. To assess the effects of phosphodiesterase type 3 and phosphodiesterase type 5 inhibitors on cardiac function and left ventricular myocardial fibrosis in catecholamine-induced myocardial injury, sildenafil and pimobendan were administered to male Wistar rats 24 hours after isoproterenol injection. Echocardiography and electrocardiogram were performed to assess kinetic and rhythm changes during 45 days of drug administration. At the end of study, type I and type III collagen were measured through immunohistochemistry analysis, and left ventricular pressure was assessed through invasive method. Echocardiography assessment showed increased relative wall thickness at 45 days in pimobendan group with significant diastolic dysfunction and increased collagen I deposition compared with nontreated positive group (3.03 ± 0.31 vs. 2.73 ± 0.28%, P < 0.05). Diastolic pressure correlated positively with type I collagen (r = 0.54, P < 0.05). Type III collagen analysis did not demonstrate difference among the groups. Sildenafil administration attenuated type I collagen deposition (2.15 ± 0.51 vs. positive group, P < 0.05) and suggested to be related to arrhythmic events. Arrhythmic events were not related to the quantity of fibrillar collagen deposition. Although negative modulation of collagen synthesis through cyclic nucleotides signaling have shown promising results, in this study, pimobendan postconditioning resulted in increased collagen type I formation and severe diastolic dysfunction while sildenafil postconditioning reduced collagen type I deposition and attenuated diastolic dysfunction.

Inotropic and lusitropic effects of incremental doses of dobutamine in dogs with right ventricular apical pacing-induced cardiac dysfunction.

This study aimed to assess the effects of incremental doses of dobutamine on diastolic function in healthy and rapid ventricular apical pacing (RVAP)-induced cardiac dysfunction anesthetized dogs. Inotropic and lusitropic effects of dobutamine (2, 4, 8, and 12 µg kg-1  min-1 ) were assessed through left ventricle (LV) pressure-volume relation and Doppler echocardiography in six female dogs before and after 8 weeks of RVAP. Peak rate of LV pressure fall (-dP/dtmin ) improved with doses >4 µg kg-1  min-1 in healthy (4,490 ± 970 vs. 3,265 ± 471 mmHg/s, p < 0.05) and >8 µg kg-1  min-1 in RVAP dogs (3,385 ± 1,122 vs. 1,864 ± 849 mmHg/s, p < 0.05) while the time constant of relaxation (tau) reduced with doses >4 µg kg-1  min-1 in both groups (healthy: 24.0 ± 3.7 vs. 28.2 ± 4.9 ms; RVAP: 32.6 ± 8.5 vs. 37.5 ± 11.4 ms, p < 0.05) comparing with baseline. Indices of relaxation (-dP/dtmin and tau) suggested preserved lusitropic response in contrast with markedly reduced indices of contractility in the RVAP group compared with healthy group at same infusion rates. Doppler echocardiography showed significant reduction of elastic recoil in failing hearts. The results of this study demonstrated maximal positive lusitropic effects of dobutamine at a dose of 8 µg kg-1  min-1 in ventricular pacing-induced cardiac dysfunction without further impairment of ventricular filling.

Hybrid surgical treatment for 2 feline cases of intrahepatic shunt.

Intrahepatic portosystemic shunt was encountered in 2 cats (10 and 5 months old) exhibiting neurological symptoms and general deterioration. Both cats were treated with coil embolization using a hybrid surgical technique combining conventional open surgery and interventional radiology techniques, achieving good postoperative outcomes (follow-up: 22 and 10 months, respectively).

Traitement chirurgical hybride pour deux cas félins de shunt intrahépatique. Un shunt portosystémique intrahépatique a été observé chez deux chats (âgés de 10 et de 5 mois) manifestant des symptômes neurologiques et une détérioration générale. Les deux chats ont été traités par une embolisation utilisant des spires à l'aide d'une technique chirurgicale hybride combinant une chirurgie ouverte conventionnelle et des techniques de radiologie d'intervention afin d'obtenir de bons résultats postopératoires (suivi : 22 et 10 mois, respectivement).(Traduit par Isabelle Vallières).

Pimobendan improves right ventricular myocardial contraction and attenuates pulmonary arterial hypertension in rats with monocrotaline-induced pulmonary arterial hypertension.

PURPOSE: The present study aimed to evaluate the therapeutic effect of pimobendan treatment for pulmonary hypertension (PH) in rats administered monocrotaline (MCT). METHODS: Fifty-four 12-week-old male Sprague-Dawley rats were injected with monocrotaline or saline solution. Serial echocardiography and right ventricular systolic pressure (RVSP) measurement via a cardiac catheter were performed. After injection of MCT, rats received oral pimobendan (MCT/pimobendan group) or no treatment (MCT group) until undergoing echocardiography and cardiac catheter insertion. RESULTS: Right ventricular systolic pressure in the MCT/pimobendan group was lower than that in the MCT group at 6 weeks. Right ventricle free wall (RVFW) myocardial systolic velocity (Sm) in the MCT group showed a reduction compared with the saline group at 2 weeks. RVFW Sm in the MCT/pimobendan group was preserved as compared with the saline group at 2 weeks. RVFW Tei index in the MCT/pimobendan group showed a reduction compared with the saline group and the MCT group at 2 weeks. Echocardiography in the MCT/pimobendan group showed improvement compared with MCT rats. CONCLUSIONS: Both a reduction in RVSP and improvement in myocardial contraction were demonstrated with administration of pimobendan in rats with PH induced by MCT. Echocardiography evaluation of systolic function seems to be useful for monitoring excess administration of pimobendan.

Unruptured right sinus of Valsalva aneurysm in a Maltese dog: a case report.

A rare case of an unruptured sinus of Valsalva aneurysm (SVA) in a 2-month-old male Maltese terrier weighing 1.0 kg with a heart murmur is presented. A right SVA and a ventricular septal defect (VSD) were diagnosed by echocardiography and cardiac catheterization. The dog died due to a worsening of his condition. The necropsy revealed the sinus of Valsalva to have a diameter of 7 mm and a VSD hole was on the opposite surface. This report is the first to describe an unruptured SVA in the right coronary cusp of a small dog.

Sequential radial and circumferential strain and oxidative stress assessment in dogs with tachycardia-induced cardiac dysfunction.

UNLABELLED: Quantitative analysis of left ventricular (LV) deformation based on two-dimensional speckle tracking echocardiography (2D STE) has increasingly been used to assess segmental and global function because conventional echocardiography is influenced by tethering effects of adjacent myocardium and cardiac translational motion. HYPOTHESIS: (1) 2D STE can be useful to detect subtle regional changes in the LV contractility during development of tachycardia-induced cardiomyopathy (TIC) to heart failure in awake dog; (2) oxidized glutathione (GSSG) and reduced glutathione (GSH) levels are associated with the development of its respective segmental wall motion abnormalities (WMA). 6 healthy canine female Beagles were examined using 2D STE myocardial strain analysis before and for 8 weeks on week basis of rapid ventricular pacing (RVP) and at the end of study each myocardial segment were evaluated for oxidative status (GSH:GSSG ratio). 2D STE showed an initial peak of reduced global radial strain at 2 weeks of RVP in all three cardiac levels analyzed in which the affected segments showed a decreased transmural fiber shortening from anteroseptal to inferior segments distributed in helical pattern suggesting impaired contractility from part of left band to apical loop of spiral muscle band while global circumferential strain showed to be reduced since the fifth week of RVP particularly in the base and midventricular levels of ascending segment in clockwise direction from lateral to inferior segments. The most affected segments are localized in the lateral to posterior wall, however, segmental oxidative stress analysis did not show correlation with WMA detected by strain. 2D STE strain demonstrated to be a reliable tool for evaluation of LV myocardial deformation in TIC canine model showing an earlier significant WMA using radial strain and later using circumferential strain which may be of importance for improvement of diagnosis and therapy in naturally occurring canine cardiomyopathy and for earlier detection of WMA after suboptimal pacemaker lead placement.