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Biomedical subjects

M D Kittleson

Publications and source records attributed to M D Kittleson.

At least 19 recordsLinked to original sources
PubMed1997

Dilated cardiomyopathy in an American cocker spaniel with taurine deficiency.

An American Cocker Spaniel with low plasma taurine concentration (< 2 nmol/mL) was presented with dyspnoea associated with pulmonary oedema and a left ventricular shortening fraction of 9%. Emergency therapy with furosemide, dobutamine, nitroglycerine and oxygen supplementation led to a good response. Chronic therapy was started with enalapril, furosemide, digoxin and taurine. Improvement in all echocardiographic indices were noted over a 22 week follow-up, most notably an increase in left ventricular shortening fraction to 20%, a decrease of E-point septal separation from 14 mm to 7 mm and marked left ventricular remodelling. This degree of improvement in myocardial function may represent a direct link between dilated cardiomyopathy in the American Cocker Spaniel and plasma taurine deficiency. Alternatively, this response may reflect a breed-related cardiomyopathy with a natural history and therapeutic response not commonly seen in the more common large breed cardiomyopathy presentations.

Animals↗
PubMed1995

Quinidine administration increases steady state serum digoxin concentration in horses.

The aim of this study was to determine if quinidine administration increases steady state serum digoxin concentration in horses. Digoxin (0.01 mg/kg q. 12 h per os) was administered to 6 horses for 7 days. Steady state was confirmed by identifying statistically indistinguishable peak and trough serum digoxin concentrations on Days 4, 5, and 6. On Day 6, serum digoxin concentration was measured at baseline and 0.25, 0.5, 1, 2, 4, 6, 8 and 12 h after digoxin administration. On Day 7, quinidine (20 g at baseline and 10 g at 2, 4 and 6 h) was administered per os and serum digoxin concentration was measured at the same time intervals. Creatinine and renal digoxin clearances were measured on Days 6 and 7. Results indicated that there was approximately a doubling of serum digoxin concentration (from mean +/- s.d. 2.57 +/- 0.96 ng/ml at baseline to 4.28 +/- 1.31 at 15 min and 5.98 +/- 1.21 ng/ml at 30 min) after starting the administration of quinidine. This elevation persisted for the 12 h after starting quinidine administration. Renal digoxin and endogenous creatinine clearances decreased but the decrease in digoxin clearance was greater. Serum quinidine concentration achieved the therapeutic range (2-6 micrograms/ml) in 5 of the 6 horses. In summary, similar to findings in other species, quinidine administration increases steady state serum digoxin concentration in horses and this occurs, at least in part, due to a decrease in renal digoxin clearance. Some of the decrease in renal clearance is due to decreased glomerular filtration which is dissimilar to findings in other species.

Animals↗
PubMed1993

Cor triatriatum dexter in two dogs.

Cor triatriatum dexter is a congenital heart defect in which the embryologic right sinus venosus valve persists as a septum within the right atrium. Cor triatriatum dexter was diagnosed in 2 dogs on the basis of clinical signs, two-dimensional echocardiography, and cardiac catheterization. In 1 of the dogs, the condition was successfully treated by surgical resection of the intra-atrial septum. In the second dog, the defect was associated with an incomplete persistent cranial left vena cava and Ebstein's anomaly; surgery was declined.

Animals↗
PubMed1993

The acute haemodynamic effects of captopril in dogs with heart failure.

The acute effects of three doses of captopril (12.5, 25, and 50 mg [approximately 0.5, 1.0, and 2.0 mg/kg]) on several haemodynamic variables and plasma aldosterone concentration were investigated in four dogs with experimentally produced heart failure (rapid ventricular pacing) and one dog with dilated cardiomyopathy. Haemodynamic variables were measured with a Swan-Ganz thermodilution catheter and an indwelling carotid artery catheter at baseline and 1, 2, and 4 h after drug administration. A statistically significant (P < 0.05) decrease in peripheral vascular resistance was observed 1 and 2 h following the 12.5 mg dose. A significant and large enough decrease in peripheral vascular resistance to produce a significant decrease in mean systemic arterial blood pressure was observed 1 and 2 h after administering 25 and 50 mg of captopril. A mild but significant increase in cardiac output was observed 1 h after each dose. The drug effect on systemic arterial blood pressure lasted less than 4 h. No statistically significant changes were observed for the group in pulmonary capillary wedge pressure, right atrial blood pressure, or plasma aldosterone concentration at any time. We conclude that the acute haemodynamic benefits provided by captopril administration were mild and due primarily to arteriolar dilation. Doses of approximately 1-2 mg/kg produced slightly greater arteriolar dilation than an approximate dose of 0.5 mg/kg. The drug effect was short-lived, lasting less than 4 h.

Administration, Oral↗
PubMed1992

Clinical findings in cats with dilated cardiomyopathy and relationship of findings to taurine deficiency.

Between October 1986 and September 1988, 37 cats with moderate to severe idiopathic myocardial failure (dilated cardiomyopathy) were evaluated prospectively. Low plasma taurine concentration and diet history including foods that can cause taurine deficiency were documented in most of the cats. Comparison with a retrospectively studied population of 33 cats with dilated cardiomyopathy diagnosed between 1980 and 1986 demonstrated that the clinical and historical findings in the 33 retrospectively studied cats were similar to those in the 37 cats studied prospectively. Clinical findings in the 2 groups were also similar to findings previously reported in the literature. Because clinical findings and diet history were similar in the prospective and retrospective groups, we believe that many cats in the latter group had diet-induced taurine deficiency. These findings support the conclusion that most cases of dilated cardiomyopathy in cats have a common etiopathogenesis related to diet and as such are preventable.

Animal Feed↗
PubMed1992

Response of cats with dilated cardiomyopathy to taurine supplementation.

Between October 1986 and September 1988, 37 cats with moderate to severe idiopathic myocardial failure (dilated cardiomyopathy) were evaluated. Clinical management of these cats was similar to that described in the literature, except that it also included administration of 500 or 1,000 mg of the sulfur amino acid, taurine per day. Early death (death within the first 30 days of treatment) occurred in 14 (38%) cats. One cat was lost to follow-up evaluation. Twenty-two cats (59%) had marked clinical and echocardiographic improvement and survived longer than 240 days. In all but 1 cat, the observed improvement in echocardiographic measurements persisted. Hypothermia and thromboembolism were positively associated with an increased risk of early death. Administration of digoxin did not significantly affect survival. All 22 cats that survived greater than 30 days remained clinically stable despite withdrawal of all medications except taurine. Administration of taurine was eventually discontinued in 20 of the 22 cats and adequate taurine intake was thereafter provided for in the food. The clinical response and 1-year survival rate of 58% (21 of 36 cats with a known outcome) in the taurine-treated group represents a marked improvement, compared with a 1-year survival rate of 13% (4 of 31 cats with a known outcome) in a retrospectively evaluated population of 33 cats with dilated cardiomyopathy.

Animal Feed↗
PubMed1991

The efficacy and safety of milrinone for treating heart failure in dogs.

Milrinone has been studied in a variety of situations. In experimental dogs it has been documented to increase contractility to a similar degree as beta-receptor agonists and to produce mild arteriolar dilation in dogs. In canine patients with heart failure, milrinone produces demonstrable improvement in echocardiographic ventricular function and hemodynamic variables. In addition, it improves clinical signs in these patients, improving their quality of life. Milrinone is superior to digoxin as evidenced by the improvement in clinical signs noted in dogs that were unresponsive or no longer responding to digoxin administration. There is no doubt that milrinone improves short-term prognosis and in so doing prolongs life. Many of the patients that the author has observed would not have gone home without the benefits of milrinone. Milrinone's effects on long-term survival cannot be assessed, but its effects on survival time are certainly not dramatic enough to be evident without a comparison population. Therefore, milrinone administration should be considered palliative, as is administration of all other cardiovascular medications for heart failure. In addition to its beneficial effects, milrinone also appears to be relatively safe when compared with the alternative of digoxin administration. Fatal events attributable to milrinone administration are rare, and those directly attributable to enhanced ventricular arrhythmia can generally be avoided by monitoring an electrocardiogram after initial milrinone administration commences. Milrinone does not increase the incidence of sudden death in Doberman Pinschers. It is possible that a small number of dogs with mitral regurgitation may develop mitral chordal rupture. For this reason and possibly others, milrinone probably will not be indicated in early heart failure due to mitral regurgitation when heart failure is readily responsive to diuretic administration. The risk-to-benefit ratio turns markedly in the favor of milrinone administration in the dog with mitral regurgitation that is partially or completely refractory to other cardiovascular drugs. Milrinone appears to be a more effective and safer positive inotrope for long-term treatment of dogs with congestive heart failure than drugs currently available. The author and all the investigators involved in the milrinone clinical trials hope that it will soon be available for use by the veterinary community.

Animals↗
PubMed1988

Evaluation of a combination of xylazine, ketamine, and halothane for anesthesia in llamas.

Anesthesia induced by use of a combination of xylazine, ketamine, and halothane, under conditions of spontaneous and mechanically controlled ventilation, was evaluated in 5 llamas positioned in dorsal recumbency. Using chronically implanted catheters, systemic arterial blood pressure, pulmonary arterial pressure, right atrial pressure, heart rate and rhythm, cardiac output, blood pH and gas tensions, body temperature, and respiratory rate were measured before anesthesia induction (baseline), throughout the anesthetic period, and for 1 hour into the recovery period. During anesthesia, llamas undergoing spontaneous ventilation developed hypercapnia and respiratory acidosis. Cardiovascular function was decreased during both types of ventilation. The combination of xylazine, ketamine, and halothane in various doses and 2 ventilation procedures (spontaneous and controlled) provided a reliable method for general anesthesia in llamas, but marked cardiovascular depression developed during anesthesia maintenance with halothane. Spontaneous ventilation resulted in potentially clinically important respiratory acidosis.

Anesthesia, General↗
PubMed1987

Myocardial failure in cats associated with low plasma taurine: a reversible cardiomyopathy.

Thousands of pet cats die each year with dilated cardiomyopathy, the cause of which is unknown. Although taurine is present in millimolar concentrations in the myocardium of all mammals, taurine depletion has not previously been associated with a decrease in myocardial function in any species. In this study, low plasma taurine concentrations associated with echocardiographic evidence of myocardial failure were observed in 21 cats fed commercial cat foods and in 2 of 11 cats fed a purified diet containing marginally low concentrations of taurine for 4 years. Oral supplementation of taurine resulted in increased plasma taurine concentrations and was associated with normalization of left ventricular function in both groups of cats. Since myocardial concentrations of taurine are directly related to plasma concentrations and low plasma concentrations were found to be associated with myocardial failure in cats, a direct link between decreased taurine concentration in the myocardium and decreased myocardial mechanical function is proposed.

Animals↗
PubMed1987

Early and late global and regional left ventricular function after experimental transmural myocardial infarction: relationships of regional wall motion, wall thickening, and global performance.

Experimental myocardial infarction of the posterolateral wall of the left ventricle was produced in dogs by injecting 80 micron microspheres into the left circumflex coronary artery to determine changes in regional myocardial function after infarction, to examine how the changes in regional myocardial function relate to the changes in global left ventricular function, and to examine the relationship between regional wall motion and wall thickening after myocardial infarction. Serial measurements of global ventricular and regional myocardial function were made in six dogs before and during 20 days after infarction, with the use of M-mode echocardiography and chronic Swan-Ganz catheter implantation. One hour after infarction, stroke volume index had decreased 49% from baseline, percent fractional shortening had decreased 52%, lateral wall motion had decreased 80%, and lateral wall thickening had decreased 100%. By 6 days after infarction, stroke volume index had increased 41% from its low point, percent fractional shortening had increased 34%, and lateral wall motion had increased 100% toward but not to baseline. Lateral wall thickening did not return following infarction. Peak and end-systolic circumferential wall stresses and systemic arterial blood pressure remained stable. End-systolic diameter increased acutely (36%) after infarction and did not change during the 20-day time period, while end-diastolic diameter gradually increased, resulting in the increase in percent fractional shortening. In conclusion, after posterolateral wall infarction, wall motion can return without an improvement in regional myocardial function, presumably because the infarcted region stiffens, allowing it to be pulled inward.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Neurohumoral and cardiopulmonary response to sustained submaximal exercise in the dog.

Neurohumoral, cardiovascular, and respiratory parameters were evaluated during sustained submaximal exercise (3.2 km/h, 15 degrees elevation) in normal adult mongrel dogs. At the level of activity achieved (fivefold elevation of total body O2 consumption and threefold elevation of cardiac output), significant (P less than 0.05) increases in plasma norepinephrine and epinephrine concentration (from 150 +/- 23 to 341 +/- 35 and from 127 +/- 27 to 222 +/- 31 pg/ml, respectively) were present, as well as smaller but significant increases in plasma renin activity and plasma aldosterone concentration (from 2.2 +/- 0.3 to 3.1 +/- 0.6 ng X ml-1 X h-1 and from 98 +/- 8 to 130 +/- 6 pg/ml, respectively). Plasma arginine vasopressin increased variably and insignificantly. The cardiovascular response (heart rate, systemic arterial and pulmonary arterial pressures, left ventricular filling pressure, and calculated total peripheral and pulmonary arteriolar resistance) closely paralleled that of human subjects. Increased hemoglobin concentration was induced by exercise in the dogs. The ventilatory response of the animals was characterized by respiratory alkalosis. These data suggest similarities between canine and human subjects in norepinephrine, plasma renin activity, and plasma aldosterone responses to submaximal exercise. Apparent species differences during submaximal exertion include greater alterations of plasma epinephrine concentration and a respiratory alkalosis in dogs.

Aldosterone↗