Evaluation of aging on muscle blood flow in conscious healthy dogs by duplex Doppler ultrasonography

According to a study conducted on a population of 9,248 subjects, cardiac diseases are the second most prevalent cause of death in the dog. During the last decades, a common scenario has been the increase on life expectancy of dogs. The exact relationship between the negative modifications of cardiovascular function and the development of specific cardiovascular diseases is difficult to ascertain, and also, the effect of age per se on vascular impedance is important. It may result in limited cardiovascular reserve under conditions of increase demand in senescent animals. To evaluate the effect of age on the peripheral vasculature specifically, the objective of this study was to compare parameters of the regional blood flow as well as compliance and resistance indexes in the femoral arterial system of younger and older conscious healthy dogs by duplex Doppler ultrasonography. The data were collected from 16 mixed-breed dogs divided into two groups: young and old healthy dogs. In all dogs Doppler spectra blood flow patterns of the femoral artery were triphasic. Significant differences were not found between the parameters measured for young and old groups. Despite this, the average value of femoral flow volume in the older group was approximately 50% lower than the younger group. This finding could play an important role in limiting exercise response with age. In order to validate these speculations, further studies should be performed in aged dogs.     

Evaluation of nonunion fractures in dogs by use of B-mode ultrasonography, power Doppler ultrasonography, radiography, and histologic examination

OBJECTIVE: To investigate the use of ultrasonography to assess nonunion of fractures in dogs and to compare results of ultrasonography, radiography, and histologic examination. SAMPLE POPULATION: 8 nonunion fractures in 6 dogs (1 each in 5 dogs and 3 in 1 dog); dogs ranged from 7 to 94 months of age and weighed 6 to 30 kg. PROCEDURES: Diagnostic assessment consisted of complete clinical and orthopedic examinations, radiography, B-mode (brightness mode) ultrasonography, and power Doppler ultrasonography. Biopsy samples were obtained during surgery for histologic examination. They were stained with H&E and immunolabeled by use of anti-CD31 antibodies. Correlations of power Doppler score, power Doppler count, vessel area, and radiographic prediction with the mean number of vessels counted per hpf were derived. RESULTS: Radiographically, 7 of 8 nonunion fractures were diagnosed as atrophic and were therefore estimated to be nonviable. Vascularity of nonunion fractures during power Doppler ultrasonography ranged from nonvascularized to highly vascularized. Absolute vessel count during histologic examination ranged from 0 to 63 vessels/hpf; 5 nonunion sites had a mean count of > 10 vessels/hpf. Vascularity during power Doppler ultrasonography was highly correlated with the number of vessels per hpf, whereas the correlation between the radiographic assessment and histologic evaluation was low. CONCLUSIONS AND CLINICAL RELEVANCE: Radiographic prediction of the viability of nonunion fractures underestimated the histologically assessed vascularity of the tissue. Power Doppler ultrasonography provided a more accurate estimation of the viability of the tissue and therefore the necessity for debridement and autografts during revision surgery.     

Spectral waveform analysis of major arteries in conscious dogs by Doppler ultrasonography

Normal values of arterial blood flow velocity and waveforms in major arteries of 10 healthy conscious Beagle dogs were determined using Doppler ultrasonography. Peak systolic, early diastolic, and end-diastolic velocities of the basilar artery, common carotid artery, abdominal aorta, external iliac artery, femoral artery, and peak ejection velocity of the valvular aorta were evaluated. Pulsatility index (PI) of the basilar artery and blood pressure were recorded. All arteries had a high-resistance flow pattern with triphasic flow velocity except the basilar artery, which had a low-resistance pattern. Mean peak systolic velocities of the basilar artery, common carotid artery, abdominal aorta, external iliac artery, and femoral artery were 72 +/- 19, 115 +/- 17, 121 +/- 24, 105 +/- 25, and 110 +/- 17 cm/s, respectively. The PI of the basilar artery and peak ejection velocity of the valvular aorta were 1.37 +/- 0.13 and 96 +/- 16 cm/s, respectively. Mean systolic and diastolic blood pressures were 137 +/- 13 and 78 +/- 15 mmHg, respectively. Present findings may be used as references in future studies on vascular diseases and hemodynamics in dogs.     

Measurement of cardiac output by transesophageal Doppler ultrasonography in anesthetized dogs: comparison with thermodilution

Thermodilution (TD) is the standard method for cardiac output (CO) monitoring in human medicine. Although called the ‘gold standard’, TD is related to numerous complications and data misinterpretations. Recently, a noninvasive, continuous, ultrasound‐based technique for CO measurement has been developed (Hemosonic 100, Arrow Intl). This study compared transesophageal Doppler ultrasonography (TED) for measuring CO with TD in anesthetized dogs. In this study, ten dogs were used to simultaneously measure CO by TED and TD. All dogs were pre‐medicated with acepromazine at 0.1 mg kg^?1 IM, induced with thiopental at 10 mg kg^?1 IV, and maintained on isoflurane at end‐tidal concentrations of 1.3%. Baseline and four different levels of CO were used for comparison. Low CO levels were induced by caudal vena cava occlusion. High CO levels were induced by the constant IV infusion of dopamine, dobutamine, or norepinephrine. Each level of CO allowed one comparison between TED and TD. Forty‐nine paired comparisons of CO were determined ranging from 0.73 to 10.9 L minute^?1. Simple linear regression was used to determine the correlation between the two techniques. Correlation coefficient (r²) was 0.53. Bland and Altman statistical method was used for assessing agreement between the two methods. The difference between the TD and TED when all data were included was 0.82 (bias) ± 1.63 L minute^?1 (mean ± SD). At low CO levels (baseline and caudal vena cava occlusion), the correlation coefficient was 0.77, bias was 0.35 ± 0.64 L minute^?1. At high CO levels (dopamine, dobutamine, or norepinephrine), the correlation coefficient was 0.39. It was concluded that TED was not a reliable monitoring method in determining CO when positive inotropes were used. TED might have importance in situations of low CO values; however, further investigation is warranted.     

Evaluation of drug-induced prostatic involution in dogs by transabdominal B-mode ultrasonography

The relative antiandrogen-induced prostate involution activity of the newly synthesized hydroxyflutamide pro-drug was compared with that of flutamide in 25 Beagles. Secondary antiandrogen activity of both drugs on the testes and mammary tissue was investigated. Daily oral administration of both compounds at 2 dosages (ie, 2.5 and 5.0 mg/kg of body weight) during a 7-week period was monitored by transabdominal ultrasonography of the prostate twice a week. Cross-sectional area estimates of the prostate gland calculated from oblique dorsoventral, and transverse sonographic measurements were diminished significantly in some of the treated dogs as early as day 14 of drug administration. All treated dogs had significant differences in reduction by day 47. Involution was related directly to dose (P less than 0.05), but no difference was observed between test compounds. Differences in secondary antiandrogen activity were not remarkable. Flutamide was not found to have any activity advantage in vivo over hydroxyflutamide. It was concluded that ultrasonography can be a highly effective means of monitoring prostate size, and of monitoring drug-induced involution over time.     

Estimation of left ventricular filling pressure by Doppler echocardiography in dogs with pacing-induced heart failure

BACKGROUND: Congestive heart failure (CHF) is a common clinical syndrome characterized by elevated filling pressure. HYPOTHESIS: Doppler echocardiographic (DE) variables of left ventricular (LV) filling can predict a decline of LV end-diastolic pressure (LVEDP) induced by acute preload reduction in dogs with compensated CHF. ANIMALS: Five male hound dogs. METHODS: Dogs previously instrumented with a transvenous cardiac pacemaker and a LV pressure gauge were paced at 160-180 bpm to induce mild CHF characterized by LVEDP > 20 mmHg. LVEDP and 9 DE variables of LV filling derived from diastolic time intervals, transmitral and pulmonary venous flow, and tissue Doppler imaging were measured simultaneously at baseline and 30, 60, 120, and 240 minutes after furosemide (4 mg/kg, IV) or placebo (0.9% saline, IV). Repeated measures analysis of variance and correlation analysis were used to determine the association between the decline of LVEDP after furosemide and DE measures of LV filling pressure (LVFP). RESULTS: Furosemide but not placebo decreased LVEDP (P < .001). The ratio of early transmitral flow velocity to LV isovolumic relaxation time (E : IVRT) predicted LVEDP best (R(2)= .50; P < .001). Correlations were also found between LVEDP and IVRT, E, ratio between E and late diastolic transmitral flow velocity (E : A), and early diastolic velocity of the mitral annulus (Ea). The ratio of E to Ea (E : Ea) was not useful in the prediction of LVEDP in this model. CONCLUSION AND CLINICAL IMPORTANCE: E : IVRT can be used to predict LVFP in dogs with mild left-sided CHF induced by rapid pacing.     

Evaluation of oscillometric and Doppler ultrasonic methods of indirect blood pressure estimation in conscious dogs

To assess the accuracy and precision of indirect measurements of systemic arterial blood pressure (BP), results obtained with an oscillometric device (BPo) and a Doppler ultrasonic device (BPud) were compared with those obtained by direct radiotelemetry (BPrt) in 12 conscious beagles. The correlation between indirectly obtained and directly measured values for BP parameters ranged widely for the different indirect methods and sites of cuff placement, with R2 between 0.001 and 0.901. Both indirect methods underestimated all BP parameters, the degree of underestimation increasing at higher values for the BP. The highest correlation occurred when estimates were the average of 5 values consecutively obtained with the oscillometric device and cuff placement at the coccygeal artery (R2 = 0.854 for mean BPo, 0.886 for systolic BPo, and 0.901 for diastolic BPo; P < 0.0001 for all parameters) or with the ultrasonic Doppler device at the metatarsal arteries (R2 = 0.810 for systolic BPud; P < 0.0001). Multiple consecutively obtained values are advised, as this approach improves the reliability of indirect BP measurements. The strong correlation between directly measured values and estimates derived as the average of 5 consecutive indirectly obtained values indicates that the latter approach provides a useful estimate of BP in conscious dogs and is likely to be useful in monitoring disease progress and treatment in dogs with abnormal BP.     

Color and power Doppler ultrasonography for characterization of splenic masses in dogs

Benign and malignant splenic masses can appear similar on B-mode imaging, making ultrasound sensitive but not specific in their diagnosis. Our goal was to characterize color and/or power Doppler characteristics of vasculature within and adjacent to a splenic mass, which would distinguish benign vs. malignant lesions. The hypothesis was that malignant splenic masses will have altered vascular patterns compared with benign masses. Color and power Doppler cineloops evaluating the vasculature within the mass and normal splenic parenchyma were obtained in sagittal and transverse planes using a standardized protocol. Categories of evaluation included presence of peritoneal effusion, a large aberrant or tortuous vessel within the mass, relative blood flow within the mass compared with normal parenchyma, and path of vessels in the adjacent parenchyma entering into the mass. All patients had histopathologic or definitive cytologic diagnosis. Thirty-one dogs were included. There were 13 malignant masses and 18 were benign. Peritoneal effusion was significantly associated with malignancy (P = 0.0007). Presence of an aberrant or tortuous vessel within the mass was nearly significant (P = 0.059). There was no significant difference in any of the color or power Doppler blood flow evaluations. Ultrasonographic findings of a splenic mass and peritoneal effusion may indicate malignancy. The presence of an aberrant vessel within a splenic mass could suggest malignancy; however more data are needed.     

Validity and reliability of Doppler ultrasonography and direct arterial blood pressure measurements in anaesthetized dogs weighing less than 5 kg

Objective

To assess the validity and reliability of Doppler ultrasonography (DOP) as compared with invasive arterial blood pressure measurements in anaesthetized dogs weighing less than 5 kg.

Evaluation of oscillometric and Doppler ultrasonic devices for blood pressure measurements in anesthetized and conscious dogs

Two non-invasive blood pressure (NIBP) devices (oscillometry and Doppler) were compared to invasive blood pressure using a Bland–Altman analysis, in anesthetized and conscious dogs. When considering the systolic arterial pressure only during general anesthesia, both NIBP devices slightly underestimated the systolic arterial blood pressure however the precision and the limits of agreement for the Doppler were of a greater magnitude. This indicates a worse clinical performance by the Doppler. The performance of both NIBP devices deteriorated as measured in conscious animals. In general, for the oscillometric device, determination of invasive diastolic and mean arterial pressures was better than the invasive systolic arterial pressure. Overall, the oscillometric device satisfied more of the criteria set by the American College of Veterinary Internal Medicine consensus statement. Based upon these results, the oscillometric device is more reliable than the Doppler in the determination of blood pressure in healthy medium to large breed dogs.     

Diagnostic value of echo-Doppler and tissue Doppler imaging in dogs with pulmonary arterial hypertension

BACKGROUND: Diagnosis of pulmonary arterial hypertension (PAH) relies on Doppler measurement of pulmonic and tricuspid regurgitation (TR). However, these are not always detectable. HYPOTHESIS: Tissue Doppler imaging (TDI), a novel noninvasive ultrasound technique, provides indirect but sensitive and specific assessment of elevated systolic pulmonary artery pressure (SPAP) in dogs. ANIMALS: One hundred and five dogs with TR. METHODS: Prospective observational study. Dogs were categorized as presenting normal (group 1, n = 45), mildly increased (group 2, n = 19), or moderately to severely increased (group 3, n = 41) SPAP, based on TR peak velocities (< 2.5, 2.5-3.0, and > 3.0 m/s, respectively). Ten quantitative echo-Doppler- and TDI-derived variables were assessed, including the main pulmonary arterial diameter to aortic diameter ratio, pulmonary flow acceleration time, and acceleration-to-ejection time ratio, the Tei index of right ventricular function, and 6 longitudinal basal right ventricular TDI variables. RESULTS: A significant correlation was observed between SPAP and each of the 10 tested variables (P < .05). Conventional echo-Doppler variables were less discriminating than the TDI for predicting increased SPAP. The combined systolic and diastolic right TDI index had the highest sensitivity and specificity (89% and 93% respectively, for a cutoff of 11.8 cm/s) and could discriminate between dogs in group 1 from dogs in group 2. CONCLUSIONS AND CLINICAL IMPORTANCE: TDI provided effective predictors of systolic PAH and demonstrated that both alterations in right-sided systolic and diastolic myocardial function can occur with mild increases in SPAP.     

Evaluation of red cell distribution width in dogs with pulmonary hypertension

ObjectivesTo compare red cell distribution width (RDW) between dogs with different causes of pulmonary hypertension (PH) and a control dog population to determine whether RDW was correlated with severity of PH as measured by echocardiography. A further aim was to determine the prognostic significance of increased RDW for dogs with PH.AnimalsForty-four client-owned dogs with PH and 79 control dogs presented to a single tertiary referral institution.MethodsSignalment, clinical pathological and echocardiographic data were obtained retrospectively from the medical records of dogs with PH, and RDW measured on a Cell-Dyn 3500 was compared between dogs with pre- and post-capillary PH and a control population. Referring veterinary surgeons were contacted for follow-up information and Kaplan–Meier analysis was conducted to investigate differences in survival time between affected dogs with different RDW values.ResultsThe RDW was significantly greater in dogs with pre-capillary PH compared to control dogs. There was no difference in median survival times between dogs with PH divided according to RDW values. The RDW was positively correlated with mean corpuscular volume and haematocrit in dogs with PH, but did not correlate with echocardiographic variables.ConclusionsAn association was found between dogs with PH and increased RDW; however there was considerable overlap in values between control dogs and dogs with PH. The RDW was not associated with survival in this study.     

Evoked potentials induced by transcranial stimulation in dogs

Evoked potentials were induced by transcranial stimulation and recovered from the spinal cord, and the radial and sciatic nerves in six dogs. Stimulation was accomplished with an anode placed on the skin over the area of the motor cortex. Evoked potentials were recovered from the thoracic and lumbar spinal cord by electrodes placed transcutaneously in the ligamentum flavum. Evoked potentials were recovered from the radial and sciatic nerves by surgical exposure and electrodes placed in the perineurium. Signals from 100 repetitive stimuli were averaged and analyzed. Waveforms were analyzed for amplitude and latency. Conduction velocities were estimated from wave latencies and distance traveled. The technique allowed recovery of evoked potentials that had similar characteristics among all dogs. Conduction velocities of potentials recovered from the radial and sciatic nerves suggested stimulation of motor pathways; however, the exact origin and pathway of these waves is unknown.     

Quantitative evaluation of contrast enhanced transcranial Doppler signal using galactose based echo-contrast agent in dogs

Transcranial Doppler ultrasonography (TCD) is hindered by insufficient ultrasound penetration through the temporal bone. The use of echo-contrast agents to enhance the Doppler signal is an important step toward the solution of this problem. The aim of the present study was to investigate the tolerability and diagnostic value of the intravenous echo-contrast agent, Levovist. Levovist was administered intravenously in 8 dogs with two doses (0.2 and 0.3 ml/kg) at different concentrations (300 and 400 mg/ml). In right middle cerebral artery (RMCA), the duration and degree of the signal enhancement were measured by TCD. All 32 administrations of Levovist produced an increase in TCD signal of the RMCA without complications. The first assessable pulse curve could be seen on the screen after 4 to 7 seconds after injection. There was no significant difference of latency period between different concentration and dosage. The signal amplitude was increased homogeneously by more than 30 dB when 0.3 ml/kg with 300 mg/ml concentration of Levovist and 0.2 and 0.3 ml/kg with 400 mg/ml concentration were administered. There was no significant difference in the duration of optimal contrasting between 0.3 ml/kg with 300 mg/ml concentration of Levovist and 0.2 and 0.3 ml/kg with 400 mg/ml concentration. The duration of the signal enhancement was 144 to 422 seconds, depending on the degree of concentration and dose of administration. Optimal TCD signal enhancement of RMCA was obtained using 0.3 ml/kg with 300 mg/ml concentration of Levovist in dogs, which is considered to provide quality visualization.     

Evaluation of quantified contrast-enhanced color and power Doppler ultrasonography for the assessment of vascularity and perfusion of naturally occurring tumors in dogs

OBJECTIVE: To investigate subjective and computerized methods of evaluation of color Doppler (CD) and power Doppler (PD) ultrasonographic images (obtained before and after administration of contrast medium) for quantitative assessment of vascularity and perfusion of various naturally occurring tumors in dogs. SAMPLE POPULATION: 34 tumors in 34 dogs. PROCEDURE: Tumors in dogs were examined via CD and PD ultrasonography before and after i.v. injection of a microbubble contrast agent (pre- and postcontrast examinations, respectively). Images were digitized for subjective assessment of vessel density and vascular pattern and computer-aided assessment of parameters of vascularity (fractional area [FA]) and perfusion (color-weighted FA [CWFA] and mean color-weighted FA [CWFA] and mean color level). RESULTS: With both analysis methods, more vessels were identified in precontrast PD ultrasonographic images than in precontrast CD ultrasonographic images. Moreover, compared with values for precontrast PD ultrasonography, FA, CWFA, and mean color level were higher for postcontrast PD ultrasonography. In postcontrast images, there was a significant association between vessel densities determined through subjective and computerized assessments. Although sample size was small, vascularity of squamous cell carcinomas was significantly greater than that of other tumor types. Ten of the 19 softer than issue that sarcomas had low vessel density with minor contrast enhancement. With increasing gross tumor volume, FA and CWFA decreased for all Doppler ultrasonographic methods. CONCLUSIONS AND CLINICAL RELEVANCE: Higher values of the ultrasonographic parameters representing vascularity and perfusion of tumors in dogs were determined via PD ultrasonography after administration of contrast medium than via PD or CD ultrasonography without administration of contrast medium.     

Evaluation of gallbladder volume and contraction index with three-dimensional ultrasonography in healthy dogs

Three-dimensional (3D) ultrasonography has been shown to be an accurate and appropriate tool for measurement of gallbladder volume in humans. Therefore, we applied this novel technique for the first time to study fasting and postprandial gallbladder volume in 10 healthy dogs and compared the results with those of 2-dimensional (2D) ultrasonography. Fasting gallbladder volumes determined by 3D ultrasonography were significantly higher than corresponding volumes determined by 2D ultrasonography (P<0.01). Additionally, gallbladder volumes were significantly decreased in the postprandial state compared with the fasting state using 3D ultrasonography (P<0.001), but 2D ultrasonography showed no significant difference (P=0.189). The Gallbladder contraction index was higher in 3D ultrasonography than 2D ultrasonography; however, it did not reach statistical significance (P=0.25). In conclusion, 3D ultrasonography was able to measure gallbladder volume in healthy dogs in this study. It is suggested that 3D ultrasonography can be used to accurately estimate gallbladder volume and contractility.     

Doppler echocardiographic evidence of pulmonary hypertension in dogs: a retrospective clinical investigation

Pulmonary hypertension (PH) decreases resistance to fatigue and life expectancy. The aim of this study was to correlate some indirect Doppler indices of PH with tricuspid and pulmonary regurgitation criteria and to relate PH on different indices with the severity of clinical signs. Furthermore the pathogenetic mechanisms associated to PH development were discussed. Dogs with Doppler echocardiographic evidence of PH diagnosed by assessment of pulmonary and tricuspid regurgitant jet velocity were selected, their clinical records were reviewed and a clinical score was computed. Seventeen cases of PH were identified. The degree of PH was assessed based on systolic or diastolic pulmonary pressure and the indirect Doppler indices (AT/ET and Tei Index) were calculated; data were statistically evaluated. Indirect Doppler indices were calculated also in a control group of seven healthy dogs. The most common clinical signs were coughing, dyspnea and syncope; the most common condition associated to PH development was the left-sided valvular heart disease. A significant positive correlation was found between Tei Index and both the systolic pressure and the severity of PH while no correlations were found between PH on different indices and clinical score and/or severity of clinical signs. Results of this study suggest that Tei-index could be an useful support not only to reveal PH but also to give information on the severity of PH. The clinical picture in dogs with PH is apparently unpredictable and not strictly correlated with the severity of PH.