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Biomedical subjects

C A Calvert

Publications and source records attributed to C A Calvert.

At least 19 recordsLinked to original sources
PubMed2001

Results of ambulatory electrocardiography in overtly healthy Doberman Pinschers with equivocal echocardiographic evidence of dilated cardiomyopathy.

OBJECTIVE: To determine results of ambulatory electrocardiography in and outcome of overtly healthy Doberman Pinschers with equivocal echocardiographic evidence of dilated cardiomyopathy. DESIGN: Case series. ANIMALS: 44 overtly healthy (25 male, 19 female) Doberman Pinschers. PROCEDURE: 24-hour ambulatory electrocardiographic (Holter) recordings with > 90% scan quality obtained the same day that echocardiography was performed were reviewed. RESULTS: Holter recordings from 42 of 44 (95%) dogs contained ventricular premature complexes (VPC). Fifteen of 44 (34%) dogs had > 100 VPC, 9 (20%) had > 500 VPC, and 5 (11%) had > 1,000 VPC. Nonsustained (< 30 seconds) ventricular tachycardia was detected in 4 dogs. Eighteen of 27 (67%) dogs with > 100 VPC, any couplets or triplets of VPC, or ventricular tachycardia developed dilated cardiomyopathy within 1 year, compared with 8 of 17 (47%) dogs with < 100 VPC, no couplets or triplets of VPC, and no ventricular tachycardia. Of the 18 dogs that did not develop dilated cardiomyopathy within 1 year, 11 (61%) did so within 3 years. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that a high percentage of Doberman Pinschers with equivocal echocardiographic evidence of dilated cardiomyopathy will be found to have VPC during 24-hour ambulatory electrocardiography and that most will develop echocardiographic abnormalities indicative of cardiomyopathy.

Animals↗
PubMed2000

Results of ambulatory electrocardiography in overtly healthy Doberman Pinschers with echocardiographic abnormalities.

OBJECTIVE: To identify, by means of 24-hour ambulatory electrocardiography, electrocardiographic abnormalities in overtly healthy Doberman Pinschers in which results of echocardiography were abnormal. DESIGN: Clinical case series. ANIMALS: 56 (35 male, 21 female) overtly healthy Doberman Pinschers with echocardiographic evidence of cardiomyopathy on initial examination that subsequently died of cardiomyopathy. PROCEDURE: Twenty-four-hour ambulatory electrocardiographic (Holter) recordings obtained at the time of initial examination were reviewed. For all dogs, scan quality was > 90%. RESULTS: Initial Holter recordings of all 56 dogs contained ventricular premature contractions (VPC). Thirty-six (65%) dogs had > 1,000 VPC/24 h, 17 (31%) had > 5,000 VPC/24 h, and 11 (19%) had > 10,000 VPC/24 h. Fifty-four (96%) dogs had couplets of VPC, 37 (66%) had triplets of VPC, and 36 (64%) had episodes of nonsustained (< 30 seconds) ventricular tachycardia. Number of VPC/24 h during the initial Holter recordings was positively correlated with numbers of couplets and triplets of VPC and number of ventricular escape beats and negatively correlated with left ventricular fractional shortening. Twenty-eight dogs died suddenly prior to the putative onset of congestive heart failure. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that along with echocardiography, 24-hour ambulatory electrocardiography can be used to help identify overtly healthy Doberman Pinschers with cardiomyopathy.

Animals↗
PubMed2000

Positive Coombs' test results in two dogs treated with amiodarone.

Effects of amiodarone, an antiarrhythmic drug that is effective in suppressing severe ventricular arrhythmias that are refractory to other antiarrhythmic drugs, were evaluated in 2 dogs with cardiac disease. One dog was a Doberman Pinscher with cardiomyopathy that developed severe thrombocytopenia after receiving amiodarone for 7 months. The second was a Giant Schnauzer with acquired mitral valve degeneration that developed regenerative anemia after receiving amiodarone for 5 months. Results of direct Coombs' tests were positive in both dogs. Adverse effects of amiodarone are numerous; in dogs, the most common adverse effects are anorexia and hepatotoxicosis. Frequent CBC and serum biochemical analyses should be performed when amiodarone is administered with the intent of continuing the drug indefinitely.

Amiodarone↗
PubMed2000

Association between results of ambulatory electrocardiography and development of cardiomyopathy during long-term follow-up of Doberman pinschers.

OBJECTIVE: To characterize ambulatory electrocardiographic results of overtly healthy Doberman Pinschers and determine associations between those results and development of dilated cardiomyopathy. DESIGN: Cohort study. ANIMALS: 114 (58 male, 56 female) overtly healthy Doberman Pinschers without echocardiographic evidence of cardiac disease on initial examination. PROCEDURE: Echocardiograms and 24-hour ambulatory electrocardiograms (Holter recordings) were obtained initially and at variable intervals. The status (live vs dead) of all dogs was known at least 2 years and as long as 10 years after initial examination (mean [+/- SD] follow-up time, 4.33 +/- 1.84 years). Associations between development of dilated cardiomyopathy and number of ventricular premature contractions (VPC), age, and sex were determined. RESULTS: 55 dogs (48%) did not have VPC on initial Holter recordings, and only 8 dogs had > 50 VPC/24 hours. The likelihood that a dog would have VPC was associated with increasing age and being male. At least 1 VPC/24 hours, and in particular, > 50 VPC/24 hours or > or = 1 couplet or triplet of VPC/24 hours, were predictive of subsequent development of dilated cardiomyopathy. Fifty-four dogs (47%) developed dilated cardiomyopathy; 12 were still alive at the end of the study, and 42 had died. Twenty-five of these 42 dogs died after the onset of congestive heart failure (CHF), 15 died suddenly before the onset of overt CHF, and 2 died of noncardiac causes. More males developed dilated cardiomyopathy than females, and dogs that died suddenly were approximately 1 year younger than those that developed CHF. CONCLUSIONS AND CLINICAL RELEVANCE: Results of high-quality Holter recordings may be used to identify overtly healthy Doberman Pinschers that are at a high risk for dilated cardiomyopathy.

Age Factors↗
PubMed2000

Heart rate variability in Doberman Pinschers with and without echocardiographic evidence of dilated cardiomyopathy.

OBJECTIVE: To characterize the salient variables of the time-domain analysis of heart rate variability (HRV) in clinically normal Doberman Pinschers and to compare those variables with those of Doberman Pinschers with cardiomyopathy and mild to moderate myocardial failure. ANIMALS: 46 Doberman Pinschers. PROCEDURE: HRV was analyzed in the time-domain from 24-hour Holter recordings obtained from 28 Doberman Pinschers with normal echocardiograms and 18 Doberman Pinschers with echocardiograms consistent with mild to moderate myocardial failure. RESULTS: Significant differences in HRV variables between the 2 groups of dogs were not detected. The HRV was greater during the nighttime (12 AM to 6 AM), compared with the 24-hour day and an 18-hour (6 AM to 12 AM) period. CONCLUSIONS AND CLINICAL RELEVANCE: HRV of dogs with mild to moderate myocardial failure was not different from that of clinically normal dogs, because there were no disturbances of autonomic balance, baroreceptor function, and other factors that influence HRV in the dogs with cardiomyopathy, or the sensitivity of time-domain analysis was overwhelmed by normal sinus arrhythmia. The techniques now used to study HRV have important limitations, especially in dogs, and better noninvasive tests of autonomic function are needed.

Animals↗
PubMed1999

Failure of spectro-temporal mapping to detect ventricular late potentials in dogs.

OBJECTIVE: To determine whether ventricular late potentials (LP) identified by time-domain analysis (TDA) of the signal-averaged ECG could be identified by three-dimensional frequency-domain analysis (FDA). ANIMALS: 11 dogs (9 of which subsequently died suddenly) with ventricular tachyarrhythmias (10 with ventricular tachycardia) and abnormal TDA of the signal-averaged ECG. PROCEDURE: Signal-averaged ECG that were abnormal when analyzed in the time domain subsequently were processed further in the frequency domain. Correlation ratios were calculated, and spectro-temporal maps were plotted, which were then compared with control data. RESULTS: Three-dimensional FDA did not detect LP. CONCLUSIONS AND CLINICAL RELEVANCE: LP may be detectable by TDA of the signal-averaged ECG and may be a specific marker for VT and sudden death in some dogs. However, FDA by use of the method applied in this study is invalid.

Animals↗
PubMed1998

Possible ventricular late potentials in Doberman pinschers with occult cardiomyopathy.

OBJECTIVE: To determine whether ventricular late potentials, detected by means of signal-averaged electrocardiography (SAECG), were associated with sudden death in Doberman Pinschers with occult cardiomyopathy. DESIGN: Case series. ANIMALS: 39 Doberman Pinschers with occult cardiomyopathy. PROCEDURE: Cardiomyopathy was diagnosed by means of serial echocardiography and ambulatory electrocardiography; SAECG was performed 1 or more times for each dog. RESULTS: 12 dogs died suddenly; the other 27 died after developing overt clinical signs of congestive heart failure. Results of SAECG were associated with outcome, and dogs in which ventricular late potentials were detected were more likely to die suddenly. however, 5 dogs for which results of SAECG were normal (n = 2) or equivocal (3) also died suddenly. CLINICAL IMPLICATIONS: Results suggest that SAECG may be useful in predicting whether Doberman Pinschers with occult cardiomyopathy, confirmed on the basis of results of echocardiography, are at risk of dying suddenly. However, the possibility of sudden death cannot be ruled out simply because results of SAECG are normal.

Animals↗
PubMed1998

Heart rate variability.

Heart rate variability (HRV), usually performed from 24 hour ambulatory ECG recordings, measures the variability of the heart rate. Alterations in autonomic balance and baroreceptor function, increased plasma norepinephrine levels, and reduced HRV have been associated with progressive myocardial failure. Not only has reduced HRV been associated with the degree of myocardial failure, possibility of prognostic significance, but also increased sudden death risk in both ischemic and nonischemic cardiomyopathy in humans. Heart rate variability analysis in the dog is confounded by pronounced sinus arrhythmia, and whether or not this technique has clinical utility in the dog remains to be demonstrated.

Animals↗
PubMed1998

High-resolution electrocardiography.

High-resolution electrocardiography, often referred to as signal averaged electrocardiography (SAECG), has clinical utility in human medicine for detecting ventricular late potentials (LP) as predictors of future arrhythmic events, specifically reentrant type of ventricular tachycardia (VT). Time-domain analysis of the SAECG is conceptually similar to standard ECG analysis, but the primary objective is to detect LP, the marker for reentrant pathways within the myocardium. Frequency-domain analysis is investigational but provides the same information as time-domain analysis and both methods of analysis have limitations. The presence of LP has been associated with the ability to induce VT, unexplained syncope, and sudden arrhythmic death. Some cardiomyopathic dogs with VT have SAECG that appear to contain LP, and sudden death has occurred in these dogs.

Animals↗
PubMed1997

Clinical and pathologic findings in Doberman pinschers with occult cardiomyopathy that died suddenly or developed congestive heart failure: 54 cases (1984-1991).

OBJECTIVE: To determine echocardiographic, electrocardiographic, and histologic abnormalities in Doberman Pinschers with occult cardiomyopathy that died suddenly and to compare findings with those of Doberman Pinschers with cardiomyopathy that died of congestive heart failure. DESIGN: Retrospective study. ANIMALS: 14 Doberman Pinschers with occult cardiomyopathy that died suddenly (group 1) and 40 Doberman Pinschers with cardiomyopathy and congestive heart failure (group 2). PROCEDURE: Serial echocardiography and continuous, ambulatory electrocardiographic (Holter) monitoring were performed. Hearts of dogs that died suddenly were examined histologically. RESULTS: Group-2 dogs died at a significantly older age than did group-1 dogs. All dogs had echocardiographic abnormalities, but changes were more severe in group-2 than in group-1 dogs. Ventricular tachyarrhythmias were documented in all dogs. Group-1 dogs were more likely to have episodes of sustained ventricular tachycardia than were group-2 dogs. Multifocal interstitial fibrosis and replacement of muscle fibers with collagen and fat were consistently observed in hearts from dogs that died suddenly. Ten group-1 dogs had received antiarrhythmic treatment prior to death. CLINICAL IMPLICATIONS: Occult cardiomyopathy can be identified by means of echocardiography and Holter monitoring in Doberman Pinschers. Doberman Pinschers with cardiomyopathy that had episodes of sustained (> 30 seconds) ventricular tachycardia were at risk of dying suddenly.

Animals↗
PubMed1997

Spectro-temporal mapping of the surface electrocardiogram in clinically normal dogs.

OBJECTIVES: To establish data for selected variables of the signal-averaged ECG and determine whether sedation affects segment lengths and points within the terminal QRS complex where windows began. SAMPLE POPULATION: Overtly healthy dogs with no detected abnormalities. PROCEDURE: Signal-averaged ECG (600 beats) were obtained from dogs in left-lateral recumbency, using X, Y, and Z leads with 26-gauge subdermal platinum electrodes. Frequency-domain analyses were performed by fast Fourier transform (FFT), using a post-processing computer software package. Analyses were extracted from 30-, 40-, and 50-millisecond windowed (Blackman-Harris) segments of the terminal 10 or 20 milliseconds of the QRS complex and ST segment. Correlation ratios were calculated by cross-correlation of frequency spectra of each FFT in the range of 40 to 200 Hz. The reference spectrum was the last FFT (nearest the T wave). Spectro-temporal maps were plotted for each analysis. RESULTS: Noise levels were < 1 microV. Sedation resulted in less noise and slower heart rate, but did not affect results. Correlation ratios were not different among 30-, 40-, and 50-millisecond segments, but were lower when 20 (vs 10) milliseconds of the terminal QRS was included. Spectro-temporal maps were similar in all subjects. CONCLUSIONS: Use of sedation facilitated the procedure without affecting results. Segment lengths of 40 and 50 milliseconds, beginning 10 milliseconds prior to the end of the QRS complex and analyzed in the range of 40 to 200 Hz, yielded correlation ratios > 67%, 95% of the time. CLINICAL RELEVANCE: Spectro-temporal mapping may identify dogs with ventricular late potentials (high-frequency signals commonly associated with myocardial fibrosis) that may be at increased risk of sudden death.

Acepromazine↗
PubMed1996

Diagnosis of right coronary artery to right atrial fistula in a dog using two-dimensional echocardiography.

A five-year-old boxer dog developed cardiac murmurs, complete heart block and cardiomegaly associated with vegetative bacterial endocarditis. Using two-dimensional echocardiography, vegetative lesions of the aortic valves and extension of the vegetations into the proximal right coronary artery and adjacent atrial septum were identified. The vegetation within the atrial septum appeared as a cavitated mass which protruded into the right atrium. Fistulae within the atrial septal vegetation permitting communication between the coronary artery and right atrium were observed with colour Doppler echocardiography. The dog died despite medical treatment. Post mortem examination confirmed the echocardiographic findings. Vegetative endocarditis with invasion into the right coronary artery and atrial septum producing fistulae and communication with the right atrium has not been reported previously in dogs. Doppler echocardiography proved useful in demonstrating the abnormal anatomy, intraluminal fistular blood flow and its communication with the right atrium.

Animals↗
PubMed1996

Effects of acepromazine and buprenorphine on measured indices of the signal-averaged electrocardiogram in healthy dogs.

OBJECTIVES: To determine values for indices of signal-averaged electrocardiograms (SAECG) in healthy dogs, and to determine whether sedation with acepromazine and buprenorphine would alter these indices. ANIMALS: 15 healthy adult dogs. PROCEDURE: SAECG were recorded from each dog twice: prior to sedation and immediately after sedation with acepromazine (0.01 mg/kg of body weight, IV) and buprenorphine (0.007 mg/kg, IV). Time-domain methods were used to analyze the SAECG. All indices were calculated by use of a computer. Measured indices included QRS duration, duration of low-amplitude signals in the terminal part of the QRS complex, root mean square voltages of the terminal 30 and 40 milliseconds of the QRS complex, heart rate, and high-frequency noise levels. RESULTS: We did not detect significant differences between values measured when dogs were not sedated and values measured when dogs were sedated except in regard to heart rate (P = 0.0001) and high-frequency noise levels (P = 0.0004), which were lower when dogs were sedated. Late potentials were not visually identified in SAECG from any dog in this study. CONCLUSION AND CLINICAL RELEVANCE: Sedation facilitated recording of SAECG in dogs without altering the results.

Acepromazine↗
PubMed1995

Surgical removal of heartworms from a cat with caval syndrome.

Caval syndrome was diagnosed in a 4-year-old male domestic shorthair cat with severe dyspnea attributable to chylothorax. The diagnosis of heartworm infection was made on the basis of the ultrasonographic detection of a large number of adult heartworms in the right side of the heart and positive results for modified Knott's and heartworm antigen tests. Heartworms were surgically removed through an incision in the jugular vein, using a string-type horsehair brush and an alligator forceps. All clinical signs resolved after the surgery. Although treatment with agents that would kill the adult heartworms was considered, surgical treatment was used on the cat reported here. Surgical treatment may be the method of choice for use in cats with severe or persistent clinical signs attributable to infections with large numbers of heartworms.

Animals↗
PubMed1991

Effect of medical therapy on survival of patients with dilated cardiomyopathy.

Few studies have been conducted that focus on survival as the end point of medical therapy of CHF. No vigorous studies have been conducted in dogs. It is generally accepted that diuretic therapy is an essential component of the therapy of CHF in cardiomyopathic dogs. Significant symptomatic improvement is afforded by diuretics, and acute death may be prevented. In this context diuretics can be said to improve survival. However, diuretics do not alter the natural progression of cardiomyopathy and in this context do not favorably influence long-term survival. Digitalis glycosides have been shown in humans to improve various parameters of CHF in a subset of patients with either atrial fibrillation or third heart sounds. In dogs, these gallop heart rhythms due to third heart sounds are usually associated with myocardial failure due to dilated cardiomyopathy. In spite of symptomatic improvement, no study has demonstrated an unequivocal favorable effect of digoxin on survival of patients with dilated cardiomyopathy. Likewise, there is no convincing evidence of an adverse effect on survival. Newer, powerful inotropes, such as milrinone, often demonstrate impressive short-term improvements in left ventricular function, clinical signs, and exercise tolerance in patients with CHF. However, their long-term benefits are much less impressive, they are arrhythmogenic, and they have not been shown to prolong survival. In fact, long-term milrinone therapy in humans has had an unfavorable influence on mortality. Vasodilators offer the potential advantage of increasing left ventricular performance without an associated increase in myocardial oxygen demand and cardiac rhythm disturbances. The only vigorous survival study that unequivocally demonstrated improved survival of patients with advanced CHF due to myocardial failure, including dilated cardiomyopathy, was the Consensus Trial. Survival of patients receiving enalapril was significantly better than those receiving placebo. In fact, the trial was stopped prematurely by the ethical review committee when it became obvious that the results favored the enalapril group. Although the use of beta-adrenergic blocking drugs in cardiomyopathic patients with CHF is controversial and associated with a risk of short-term deterioration of left ventricular function, their use in human medicine is gaining acceptance. Although hemodynamic and clinical evidence of improvement has been demonstrated along with withdrawal-associated deterioration, the only study purporting a beneficial effect on survival used retrospective controls.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenergic beta-Antagonists↗