Relationship between pulmonary arterial pressure and lesions in the pulmonary arteries and parenchyma, and cardiac valves in canine dirofilariasis.

The relationship between pulmonary hypertension and lesions was examined in 41 dogs infested naturally with heartworms, which consisted of 28 cases with pulmonary heartworm disease and 13 cases with caval syndrome. Pulmonary arterial pressure (PAP) was measured before and 1 or 7 days after heartworm removal with a flexible alligator forceps. In these dogs, lesions were examined after the last measurement of PAP. The mean PAP was 28.2 +/- 16.0 mmHg (10.9 to 81.4 mmHg in range) at post-removal phase. Pulmonary arterial intimal lesions, pulmonary thromboemboli, pneumonic lesions, tricuspid valvular lesions and mitral valvular lesions were macroscopically recognized in 95, 59, 39, 54 and 56% of cases, respectively. These lesions were classified by severity and the relationship with PAP was examined by the multiple correlation analysis. The multiple coefficient correlation was found the highest between PAP and thromboemboli, followed by mitral valvular lesion, tricuspid valvular lesion, and pneumonic lesion. There was no significant correlation between PAP and intimal lesions. The coefficient of determination showed the highest value in thromboemboli when one variable was used, and increased only very slightly when a variable of thromboemboli was added to those of other lesions. The cases with high PAP had fresh thromboemboli in large pulmonary arteries. From these evidences, it was concluded that thromboemboli following natural death of heartworm was the most important factor causing an increase in PAP and developing clinical signs in canine heartworm disease.     

Renal haemosiderosis in association with canine heartworm disease

Twenty-five cases of renal haemosiderosis associated with canine heartworm disease are reported. Severe intravascular haemolysis was a feature of six dogs with filariae in the right atrium and venae cavae (caval syndrome). An association between haemosiderin deposition and filarial burden was apparent in nineteen dogs not showing clinical signs of caval syndrome. The possible reasons for the sub-clinical haemolysis in canine heartworm disease are discussed with regard to current literature.     

An investigation of the role of immunologic factors in anemia associated with canine heartworm disease

Direct Coombs' antiglobulin tests were performed on 80 dogs with patent Dirofilaria immitis infection and 170 dogs negative for microfilaria of D. immitis. Presence or absence of anemia was determined by hematocrit in 55 of the heartworm negative dogs and 68 of the dogs with heartworm disease. Heartworm infected dogs showed a higher incidence (37%) of anemia than noninfected dogs (14.5%). Anemia was most prevalent in two groups of dogs with heartworm infection, one group showing vena caval syndrome (91%) and the other occult dirofilariasis (62.5%). These latter two groups of dogs also showed a significantly higher number of positive Coombs' reactions at 37 degrees C than other dogs with heartworm disease and the noninfected dogs. The number of positive Coombs' reactions at 4 degrees C among the total of 80 dogs with heartworm infection was significantly higher than that for dogs without heartworm disease. However, there was no positive correlation between anemia and the outcome of the Coombs' test at either temperature. These findings do not suggest that immunologic factors play a major role in the pathogenesis of anemia in dogs with heartworm disease.     

Postadulticide pulmonary hypertension of canine heartworm disease: successful treatment with oxygen and failure of antihistamines

Postadulticide pulmonary hypertension mechanisms and treatment with antihistamines and supplemental oxygen were studied in eight dogs with heartworm disease. To ensure severe postadulticide thromboembolism, additional heartworms (either 20 or 40 into 4 dogs each) were transplanted into naturally infected dogs before thiacetarsamide treatment. During pentobarbital anesthesia, 2 pulmonary hemodynamic studies were conducted on each dog with a sequence of baseline, hypoxia with FlO2 = 10%, hyperoxia with FlO2 = 100%, a second baseline, treatment with either diphenhydramine (D) or cimetidine (C), and another hypoxia. All dogs were pulmonary hypertensive, with each dog having a mean pulmonary arterial pressure (PPA) greater than 20 mm of Hg. Mean PPA increased from baseline conditions (25.0 +/- 4.5 SD for D and 24.3 +/- 4.4 for C) to hypoxia (28.5 +/- 4.7 for D and 28.4 +/- 3.7 for C), and decreased during hyperoxia (16.9 +/- 3.0 for D and 17.4 +/- 3.0 for C), respectively. Neither antihistamine reduced PPA at normoxia. The degree of pulmonary hypertension when breathing room air increased even more during hypoxia, and this increase was not attenuated by either antihistamine. Histamine did not appear to mediate pulmonary hypertension during postadulticide thromboembolism, nor to modify the hypoxia-mediated pulmonary hypertension at this disease stage. Because baseline PO2 was low (66.6 +/- 11.7 mm of Hg for D and 69.4 +/- 14.2 for C) and because PPA decreased during administration of oxygen, the pulmonary hypertension was mostly hypoxia-induced. In addition to the arterial lesions, much of the pulmonary hypertensive mechanism was an active and reversible vasoconstriction in response to hypoxia caused by the secondary lung disease.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pneumonitis associated with occult heartworm disease in dogs

Nine of 69 dogs with occult heartworm disease (13%) had allergic pneumonitis characterized by consistent clinical and radiographic signs. Although the clinical signs were severe, the degree of radiographic pulmonary arterial abnormalities was mild. Corticosteroid therapy resulted in rapid resolution of clinical and radiographic signs; thiacetarsamide therapy was then given without complications. This syndrome may not be recognized as heartworm-associated and may be confused with other disorders, some being associated with a poor prognosis and requiring different therapy.     

A clinical study on velocity patterns of pulmonary venous flow in canine heartworm disease

In this study, we evaluated methods of determining the velocity patterns of pulmonary venous flow (PVF) in dogs and then investigated the relationship of the patterns to cardiac functions in heartworm disease (HD) by transthoracic echocardiography (TTE). The results revealed that there was a good correlation between PVF patterns determined by transesophageal echocardiography (TEE) and TTE in animals lying on their left sides. The measurement of S and D wave velocities (PVS and PVD) by TTE was shown to allow clinical determination of the velocity patterns of PVF in dogs. The HD groups showed significant increases in PVS and PVD, and S and D wave time-velocity integrals (S-TVI and D-TVI) of the right cranial lobe PVF, when compared with the normal group, as determined by TTE (P<0.05). In contrast, the HD groups produced significant decreases in PVD and D-TVI of the right caudal lobe PVF compared with the normal group (P<0.05), and a significant increase in the ratio of S-TVI to (S-TVI + D-TVI) (P<0.05). It is, therefore, suggested that measurement of the velocity patterns of the right cranial and caudal lobe PVF could be one method of assessing the stages of obstructive lesions in the pulmonary artery.     

Relationship of pulmonary arterial pressure to pulmonary haemorrhage in exercising horses

Exercise-induced pulmonary haemorrhage (EIPH) is characterised by blood in the airways after strenuous exercise and results from stress failure of the pulmonary capillaries. The purpose of this experiment was to establish a threshold value of transmural pulmonary arterial pressure at which haemorrhage occurs in the exercising horse. Five geldings, age 4-14 years, were run in random order once every 2 weeks at 1 of 4 speeds (9, 11, 13, 15 m/s); one day with no run was used as a control. Heart rate, pulmonary arterial pressure and oesophageal pressure were recorded for the duration of the run. Transmural pulmonary arterial pressure was estimated by electronic subtraction of the oesophageal pressure from the intravascular pulmonary arterial pressure. Within 1 h of the run, bronchoalveolar lavage was performed and the red and white blood cells in the fluid were quantified. Red cell counts in the lavage fluid from horses running at 9, 11 and 13 m/s were not significantly different from the control value, but after runs at 15 m/s, red cell counts were significantly (P<0.05) higher. White cell counts were not different from control values at any speed. Analysis of red cell count vs. transmural pulmonary arterial pressure indicated that haemorrhage occurs at approximately 95 mmHg. Red cell lysis in the lavage fluid was also apparent at transmural pulmonary arterial pressures above 90 mmHg. We conclude that, in the exercising horse, a pulmonary arterial pressure threshold exists above which haemorrhage occurs, and that pressure is often exceeded during high speed sprint exercise.     

低温诱发肉鸡腹水综合征发生过程中肺血管重塑与肺动脉高压的关系

将160只15日龄雄性AA商品代肉鸡随机分为对照组((22±1.5)℃)和低温组((11±2)℃)。15~50日龄,每组每周随机取6只,以右心导管法直接测定肺动脉压(PAP),并取肺组织做石蜡切片进行Weigert-间苯二酚复红染色,分析肺血管重塑情况。50日龄时统计整个饲养过程中肉鸡腹水综合征(AS)发生率。结果显示,低温组肉鸡AS发生率(18.75%)极显著高于对照组(1.25%)(P<0.01);低温组肉鸡PAP从22日龄开始较对照组明显升高(P<0.01或P<0.05);20~50、50~100、100~200μm肺动脉结构分别从36、43、43日龄开始较对照组发生了明显的重塑(P<0.01或P<0.05)。结果表明,低温诱发肉鸡AS过程中出现了明显的PAP升高和肺血管重塑,且肺动脉高压(PH)促进了肺血管重塑,肺血管重塑加剧了PAP升高。     

东莞市犬心丝虫抗原、莱姆病抗体和犬埃里希抗体的调查报告

为了解心丝虫、莱姆病、犬埃里希氏体病在东莞市犬中的流行状况,对东莞市210份犬血清进行了心丝虫抗原、莱姆病抗体、犬埃里希抗体检测试验,试验结果:在检测的210份犬血清中,心丝虫抗原阳性0份、莱姆病抗体阳性0份,犬埃里希抗体阳性12份,犬埃里希抗体阳性率为5.71%。     

Improvement in pulmonary arterial lesions after heartworm removal using flexible alligator forceps

Improvement of pulmonary arterial lesions after heartworm removal using flexible alligator forceps was investigated by measuring pulmonary arterial pressure (PAP), and by angiographic and histopathological examinations in 11 dogs. PAP obtained immediately after worm removal corresponded well with angiographic abnormalities. In 2 dogs, high PAP immediately after worm removal fell gradually by 12 weeks, and obstructions on angiogram were resolved at 4 to 12 weeks. In 4 dogs, slightly high PAP fell to the normal range at 4 weeks, and angiographic abnormalities were considerably reduced at 4 to 12 weeks. In 5 dogs, PAP returned to normal range immediately after worm removal, and angiographic changes almost disappeared at 4 to 8 weeks. On biopsy immediately after worm removal, samples of the main pulmonary arteries showed severe intimal proliferations with villous or papillary protrusion into the lumen. Autopsy at 12 to 20 weeks indicated that the intimal protrusions were remarkably reduced as compared with the biopsy samples in all cases. However, villous intimal protrusions were seen in the caudal lobar arteries in cases with remaining alive worms. New vessels seemed to develop into thromboemboli with time. From these findings, it is clear that the pulmonary arterial lesions improved after heartworm removal, and the clinical signs disappeared following the improvement in hemodynamics. Aspirin therapy (5 mg/kg/day) for 4 weeks after worm removal in 5 dogs did not improve the intimal lesions as compared to 3 control dogs.     

Development of artificial model of caval syndrome in canine heartworm disease

In order to develop an artificial model of caval syndrome (dirofilarial hemoglobinuria), heartworm-like silicone tubes were inserted into the tricuspid valve orifice and right atrium of dogs. Fifteen to 25 tubes with some knots were inserted through the posterior vena cava in 6 dogs (knot-tube group), 7 to 12 tubes without knot (small-number group) through the jugular vein in another 5 dogs, or 25 to 35 tubes (large-number group) in yet another 5 dogs. The tubes remained in the right atrium, and a part of them protruded into the tricuspid valve orifice. The number of tubes at the tricuspid valve orifice was the greatest in the large-number group. After tube insertion, the signs of so-called "caval syndrome", such as systolic cardiac murmur, jugular pulse, anemia, and so on, were observed in almost all cases of the 3 groups, the signs were severest in the large-number group. Urine hemoglobin was detected in almost all cases of the knot-tube and large-number groups, and in 1 case in the small-number group. Ascites was observed in 1 case of the knot-tube group at 6 weeks, in 1 case of the small-number group at 7 days and in 3 cases of the large-number group at 7 days after insertion.     

An updating of the occurrence of canine heartworm disease in northern Italy

A survey was carried out in northern Italy (Veneto and Friuli Venezia Giulia Regions) to assess the extension of canine heartworm disease close to the classic hyperendemic areas of the Po Valley. A filtration test on 275 privately owned dogs showed a mean prevalence of 44%, with a peak of 55% in the Venice province. A high prevalence (17%) of occult filariosis was discovered using a serological test. These values fall within the medium-high range previously reported from other Italian areas. The provinces of Pordenone, Udine, Trieste, Treviso and Belluno, where no cases had been previously reported, were found to be infected. The distribution of the infection did not differ significantly with the dogs' origin or sex. The prevalence seemed to be influenced significantly (p<0.01) by the hosts' age, function and degree of outdoor activity, reflecting the different exposure risks.Abbreviations EDTA ethylenediaminetetraacetic acid - ELISA enzyme-linked immunosorbent assay     

Cardiopulmonary function in dogs with serious chronic heartworm disease.

Cardiopulmonary function was examined in 18 dogs with serious chronic heartworm disease showing ascites, subcutaneous edema, prostration, weakness, jaundice and so on. After surgical heartworm removal from the pulmonary arteries, 10 dogs recovered (surviving group), and 8 dogs died or were euthanatized because of poor prognosis (nonsurviving group). The number of live heartworms residing in the pulmonary arteries of the surviving group tended to be larger than that in the nonsurviving group. At necropsy, severe pulmonary arterial lesions such as thromboembolism including dead heartworms, proliferative and villous lesions and intimal hyperplasia were noticed in all dogs examined, and tended to be severer in the nonsurviving group. Heartworm-coiling around the tricuspid valve chord was found in 1 dog of the surviving group and 4 dogs of the nonsurviving group. Before heartworm removal, there was no significant difference in the mean pulmonary arterial pressure (MPAP) between the surviving and nonsurviving group. Right atrial pressure (v-wave) was higher, and the cardiac index (CI) was lower in the nonsurviving group. Arterial oxygen tension was lower in the surviving group than in the heartworm-free group, and it was lower in the nonsurviving group than in the surviving group. Carbon dioxide tension was lower in the surviving group than in the heartworm-free group. Bicarbonate concentration (HCO3-) was lower both in the surviving and nonsurviving groups than in the heartworm-free group. One week after heartworm removal, MPAP decreased (P less than 0.05), and CI and HCO3- tended to increase in the surviving group.     

Right ventricular enlargement in heartworm disease.

The size of the right ventricle of 15 dogs with spontaneous Dirofilaris immitis microfilaria was evaluated by thoracic radiography, electrocardiography, and right ventricular free wall weights. Based on electrocardiography and right ventricular weights, none of the 15 dogs had evidence of right ventricular hypertrophy. Based on radiography, only 2 of the 15 dogs had right ventricles of normal size. Right ventricular dilation in the absence of right ventricular hypertrophy was demonstrated. The right ventricle appears to dilate, prior to hypertrophy, in response to D immitis infestation.     

Pulmonary vascular response of dogs with heartworm disease.

Heartworm diseases in dogs is an infectious disease that produces pulmonary hypertension. Dogs with the early vascular changes of heartworm disease, but without the clinical cardiopulmonary signs and pulmonary hypertension, were studied. Dogs with early heartworm were identified that had an exaggerated hypertensive response to hypoxia and to postaglandin F2alpha as compared to those of normal dogs. The pulmonary hypertensive response of dogs with spontaneous heartworm disease varied widely between individuals.