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Keywords:

  • cardiology;
  • cardiomyopathy;
  • chronic valvular disease;
  • electrolytes;
  • emergency medicine

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and Methods
  5. Results
  6. Footnotes
  7. References

Objective – To characterize the clinical presentation, management, and in-hospital outcomes of dogs and cats diagnosed with acute congestive heart failure (CHF).

Design – Retrospective study of animals seen between January 2007 and May 2008.

Setting – Emergency service at a university teaching hospital.

Animals – Ninety dogs and 55 cats with CHF.

Measurements and Main Results – Patient characteristics, including age, clinical signs, clinicopathologic abnormalities, diagnostic testing, and outcome were recorded. Forty-eight of the animals already were receiving cardiac medications at the time of presentation. The most common diseases represented were chronic valvular disease and cardiomyopathies. Cats had significantly lower median body temperature at admission compared with dogs (P<0.001). The most common abnormalities were elevated lactate (64%), elevated BUN (52%), hypochloremia (31%), hyperglycemia (27%), and elevated liver enzymes (26%). Many of these became even more prevalent during hospitalization. One hundred and sixteen animals were discharged from the hospital, for a survival rate of 80%. There was no survival difference between dogs and cats (P=0.39). Dogs that developed hypokalemia during hospital stay (P=0.04) were more likely to survive compared with those without hypokalemia and initial body temperature was lower for those cats that did not survive (P=0.02). Of those that did not survive, the majority were euthanized (n=25), while 4 dogs died.

Conclusions – Dogs and cats presented to the emergency service with CHF had a high survival rate. In cats, initial body temperature was lower for those cats that did not survive. Although clinicopathologic abnormalities were common in both species, only dogs with hypokalemia had improved survival to hospital discharge.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and Methods
  5. Results
  6. Footnotes
  7. References

In both human and veterinary medicine, cardiac disease is one of the most common causes of morbidity; congestive heart failure (CHF) accounts for approximately 1 million annual human hospitalizations in the United States.1 Large human databases have been created and have provided important information on demographic factors, treatment, mortality rates, hospitalization times, and predictors of mortality.2–6 The largest of these databases are the Acute Decompensated Heart Failure National Registry (ADHERE) from the United States and, in Europe, the EuroHeart Failure Survey I and II (EHFS I and II).2–6 The ADHERE study, for example, provides data from >100,000 hospitalizations for CHF and describes clinical presentation and management.2,3 In addition, outcomes and risk factors for mortality have been described.2,3 Azotemia, hypotension, hyponatremia, age, and the presence of cancer have been associated with increased mortality in humans hospitalized with CHF.2,3,7

Few studies of a similar nature to these large human databases have been published in veterinary medicine for animals with acute CHF. One study of 59 dogs with CHF reported a mortality rate of 44% (euthanasia+died).8 That study also showed that hyponatremia and hyperglycemia were associated with an increased mortality rate.8 Some studies have included dogs and cats with acute CHF but have not reported on this subpopulation of animals separately.9–14

The large human databases have provided information that has enhanced the understanding of acute CHF and improved treatment of patients with this common disease. The purpose of this retrospective study was to characterize the clinical presentation, management, and in-hospital outcomes of dogs and cats diagnosed with acute CHF.

Material and Methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and Methods
  5. Results
  6. Footnotes
  7. References

Case selection

All dogs and cats presented to the Emergency Service that were diagnosed with CHF between January 1, 2007 and May 1, 2008 were eligible for the study. Animals were identified through a search of the computerized medical record, the Emergency Service case log, and the cardiology database. Medical records were examined to verify the clinical diagnosis of CHF, with documented fluid accumulation due to cardiac failure, using the following criteria: a diagnosis of CHF either on the cardiology consultation report or on the finalized discharge report of the medical record, along with a retrospective review of the physical examination, radiographic, and echocardiographic findings to ensure that the data in the medical record were consistent with a diagnosis of CHF. Eligible animals could have new onset CHF or decompensation of chronic previously diagnosed cardiac disease. Multiple episodes of CHF were recorded as separate events so animals with multiple CHF events were enrolled in the study more than once. Animals with cardiac disease but without documented CHF were excluded (eg, cats with arterial thromboembolism but no CHF; dogs with acute pericardial effusion but no cardiogenic ascites or pleural effusion, and animals with noncardiogenic pulmonary edema, ascites, or pleural effusion).

Data were collected from the time of admission to the time of discharge, death or euthanasia using a computerized spreadsheet that included information on signalment (species, age, sex, breed), medical history, chief owner complaint, concurrent diseases, physical examination findings at admission (body weight; body condition score; heart rate; respiratory rate; rectal temperature; presence of pulmonary crackles, a cardiac gallop, or jugular vein distension; International Small Animal Cardiac Health Council [ISACHC] Stage),15 diagnostic testing results (ECG, blood pressure, radiographic, and echocardiographic findings), laboratory data, treatment (oxygen therapy, thoracentesis, abdominocentesis, pericardiocentesis, medications, ventilation), and outcome (survived to discharge, died, or euthanized). Hypotension was defined as a systolic blood pressure <90 mm Hg. Sinus tachycardia was defined as the diagnosis of this rhythm by a cardiologist or a heart rate >160/min in dogs or >240/min in cats. Oxygen therapy was defined as ≥1 hour in an enriched oxygen environment. Body condition score was assessed on a 1–9 scale where 1 is emaciated, 5 is ideal, and 9 is obese.16,17 Clinicopathologic abnormalities were defined by a value above or below the laboratory's reference interval. All radiographs were reviewed by a board-certified radiologist and the echocardiography was performed or interpreted by a board-certified cardiologist. The ratio of the left atrial diameter to the aortic diameter was measured using standard left atrial and aortic diameters from M-mode echocardiography from a right parasternal short-axis view.18

Statistical analysis

Data were examined graphically and using the Kol-mogorov-Smirnov test. As many of the data were not normally distributed, data are presented as median (range). Survival was defined as discharge from the hospital. Comparison of all results between dogs and cats was performed with chi-square analysis (for categorical data; eg, survival between animals with and without hypokalemia) or Mann-Whitney U (for continuous data; eg, furosemide dosage between animals that did or did not survive). A P-value<0.05 was considered statistically significant. All data analyses were performed using commercial statistical software.a

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and Methods
  5. Results
  6. Footnotes
  7. References

One hundred and forty-five animals (90 dogs, 55 cats) met the inclusion criteria for the study. Nine animals were admitted >1 time. Median age of all animals was 11.3 years (0.2–22.5 y) and was not significantly different between dogs and cats (Table 1). More males than females were presented for both species (63% male; 37% female) and most (89%) were castrated or spayed (Table 1). The most common dog breeds were Doberman Pinscher (n=9), Cavalier King Charles Spaniel (n=7), Shih Tzu (n=7), Cocker spaniel (n=6), German Shepherd (n=5), Dachshund (n=4), and Yorkshire terrier (n=3). Twelve dogs were mixed breeds. Most cats were Domestic Shorthair (n=30) or Domestic Longhair (n=14). The most commonly represented cat breeds were Maine Coon cat (n=3), Ragdoll (n=3), and Siamese (n=3).

Table 1.   Signalment and physical examination findings in 145 animals presented for congestive heart failure*
ParameterAll animalsDogsCatsP-value*
  • *

    Dogs versus cats.

  • †Presented as median (range).

n1459045 
Age (y)11.3 (0.2–22.5)11.5 (0.2–17.2)10.7 (2.0–22.5)0.99
Gender   0.29
 Male91 (78 castrated)55 (45 castrated)36 (33 castrated) 
 Female54 (51 spayed)35 (32 spayed)19 (19 spayed) 
Weight (kg)7.6 (2.2–53.0)14.5 (2.2–53.0)4.5 (2.2–8.4)<0.001
Body condition score (1–9)5 (2–9)5 (2–8)4 (2–9)0.01
Heart rate (/min)160 (32–300)150 (32–273)200 (90–300)<0.001
Respiratory rate (/min)56 (16–120)48 (16–120)60 (24–98)0.009
Murmur grade   <0.001
 No murmur472720 
 I/VI431 
 II/VI1358 
 III/VI22157 
 IV/VI30246 
 V/VI23212 
 VI/VI110 
Temperature (°C)38.2 (34.9–40.2)38.3 (36.7–40.2)37.6 (34.9–38.9)<0.001
Pulmonary crackles372890.06
Cardiac gallop35728<0.001
Blood pressure (mm Hg)112 (50–200)112 (65–200)110 (50–180)0.85

Animals were presented for a number of different problems. The most common presenting complaints for dogs were breathing abnormalities (n=35), collapse (n=18), exercise intolerance (n=14), coughing/gagging (n=11), and lethargy (n=8). For cats, the most common presenting complaints were breathing abnormalities (n=36), lethargy (n=9), and hind leg paralysis (n=6). Preexisting, concurrent diseases were present in 29 animals. The most common concurrent diseases were renal disease (4 dogs, 8 cats) and hyperthyroidism (5 cats). At the time of presentation, 69 animals (50 dogs, 19 cats) already were receiving at least 1 cardiac medication (furosemide [n=59], angiotensin-converting enzyme [ACE] inhibitors [n=57], pimobendan [n=29], digoxin [n=18], calcium-channel blockers [n=13], low–molecular-weight heparin [n=12], β blockers [n=6], clopidogrel [n=5], and aspirin [n=2]).

On physical examination, the median BCS of animals was 5 (2–9), with cats having a significantly lower BCS than dogs (P=0.01; Table 1). Median heart rate (dogs, 150/min, [32–273/min]; cats, 200/min [90–300/min]; P<0.001) and median respiratory rate (dogs, 48/min [16–120/min]; cats, 60/min [24–98/min]; P=0.009) were significantly higher in cats compared with dogs, but within species, there were no differences in heart rate or respiratory rate between different underlying disease. Median body temperature was significantly lower in cats (dogs, 38.3°C [36.7–40.2°C]; cats, 37.6°C [34.9–38.9°C]; P<0.001).

The presence of cardiac murmur and murmur grade was noted for 140 of the 145 animals. Murmur grade was significantly higher in dogs compared with cats (P<0.001), with 27 dogs and 20 cats having no cardiac murmur detected by the attending emergency veterinarian at the time of presentation. ISACHC stage was established in 136 of the 145 animals: ISACHC stage 2 was present in 6 dogs and 6 cats; ISACHC stage 3a in 16 dogs and 2 cats; and ISACHC stage 3b in 61 dogs and 45 cats. Pulmonary crackles were ausculted in 37 animals (28 dogs, 9 cats; P=0.06) at the time of admission, while a cardiac gallop was noted in 35 animals (7 dogs, 28 cats; P<0.001). The results of a jugular vein examination were noted for only 10 animals at the time of hospital admission; 6 of these were noted to have jugular vein distension (5 dogs, 1 cat; P=0.39). Animals with jugular vein distention had chronic valvular disease (CVD) (n=3), congenital heart disease (n=2), and unclassified cardiomyopathy (n=1) as their underlying cardiac disease.

Clinicopathologic findings

A biochemical analysis was performed at the time of admission on 130 animals (85 dogs, 45 cats; Table 2). Dogs were significantly more likely to have hypernatremia (P=0.02), hyperkalemia (P=0.02), and an elevated alkaline phosphatase (P=0.001), while cats were more likely to have hyperchloremia (P=0.005), hypokalemia (P=0.04), hyperglycemia (P<0.001), and to have an elevated aspartate aminotransferase (P=0.001). The majority of animals (72/112; [64%]) had an elevated lactate concentration at the time of admission (2.5 mmol/L, [0.4–11.5 mmol/L]; reference interval, 0.1–1.9 mmol/L).

Table 2.   Number of animals presented for congestive heart failure that had abnormal clinicopathologic findings at the time of admission and median (range) for each parameter*
ParameterUnitsAll animalsDogsCatsP-value
  • *

    Data are reported for the 130 of 145 animals that had a serum biochemistry profile performed at the time of admission.

  • ALT, alanine aminotransferase; AST, aspartate aminotransferase; ALP, alkaline phosphatase.

  • Dogs vs cats.

  • mmol/L = mEq/L for sodium, chloride, and potassium.

n* 1308545 
Sodiummmol/L149 (123–160)147 (126–160)152 (123–158)<0.001
 Reference intervalmmol/L 140–150146–158 
  Hyponatremia 241950.12
  Hypernatremia 272340.02
Chloridemmol/L110 (84–121)109 (84–119)115 (90–121)<0.001
 Reference intervalmmol/L 106–116110–125 
  Hypochloremia 4029110.27
  Hyperchloremia 4040.005
Potassiummmol/L4.5 (3.1–6.3)4.7 (3.2–6.3)4.2 (3.1–5.7)0.001
 Reference intervalmmol/L 3.7–5.43.4–5.2 
  Hypokalemia 188100.04
  Hyperkalemia 191720.02
Magnesiummmol/L1.3 (0.6–2.2)1.2 (0.6–2.2)1.4 (0.8–1.9)0.006
 mEq/L2.5 (1.2–4.4)2.3 (1.2–4.4)2.8 (1.6–3.8)0.006
 Reference intervalmmol/L 0.9–1.31.0–1.4 
 mEq/L 1.8–2.62.0–2.7 
  Hypomagnesemia 5410.64
Urea nitrogenmmol/L12 (3–128)11 (3–128)13 (8–34)0.08
 mg/dL33 (8–357)31 (8–357)37 (21–94)0.08
 Reference intervalmmol/L 3–115–12 
 mg/dL 8–3015–33 
  Elevated urea nitrogen 6842260.26
Creatinineμmol/L114.9 (17.7–875.2)97.2 (17.7–875.2)150.3 (61.9–530.4)<0.001
 mg/dL1.3 (0.2–9.9)1.1 (0.2–9.9)1.7 (0.7–6.0)<0.001
 Reference intervalμmol/L 53.0–176.879.6–185.6 
 mg/dL 0.6–2.00.9–2.1 
  Elevated creatinine 2211110.10
Glucosemmol/L6 (3–23)5 (3–11)8 (5–23)<0.001
 mg/dL104 (55–412)95 (55–198)148 (90–412)<0.001
 Reference intervalmmol/L 4–84–7 
 mg/dL 67–13570–120 
  Hyperglycemia 35530<0.001
HematocritL/L0 (0–1)1 (0–1)1 (0–1)<0.001
 %42 (20–63)46 (23–63)39 (20–49)<0.001
 Reference intervalL/L 0–10–1 
 % 39–5531–46 
  Anemia 2010100.12
Lactatemmol/L2.5 (0.4–11.5)2.6 (0.6–11.5)2.4 (0.4–8.1)0.68
 Reference intervalmmol/L 0.1–1.90.1–1.9 
  Elevated lactate 7249230.39
ALTU/L76 (16–1016)74 (16–541)80 (28–1016)0.41
 Reference intervalU/L 14–8625–145 
  Elevated ALT 292270.43
ASTU/L43 (15–4306)42 (15–463)52 (20–4306)0.03
 Reference intervalU/L 9–545–42 
  Elevated AST 3417170.001
ALPU/L87 (11–1180)117 (22–1180)22 (11–874)<0.001
 Reference intervalU/L 12–1270–5 
  Elevated ALP 333030.001
Total bilirubinμmol/L1.7 (1.7–71.8)1.7 (1.7–6.8)1.7 (1.7–71.8)0.34
 mg/dL0.1 (0.1–4.2)0.1 (0.1–0.4)0.1 (0.1–4.2)0.34
 Reference intervalμmol/L 1.7–5.11.7–5.1 
 mg/dL 0.1–0.30.1–0.3 
  Elevated bilirubin 5230.13

The lowest or highest value for electrolyte concentrations during hospitalization was also recorded. Hyponatremia was present in 24 of 130 (19%) of animals at the time of admission but subsequently developed in 85 of 130 animals (65%; 79% of dogs, 40% of cats) during hospitalization. At admission, 40 of 130 (31%) of animals were hypochloremic but 65 of 130 animals (50%; 55% of dogs, 42% of cats) became hypochloremic during hospitalization. Hypokalemia was present in 18 of 130 (14%) of animals at admission but developed in 56 of 130 animals (43%; 39% of dogs, 51% of cats) at some point during hospitalization. At admission, BUN and creatinine were elevated in 68 of 130 (52%) and 22 of 130 (17%) animals, respectively, but developed during hospitalization in 89 of 130 (69%; 63% of dogs, 82% of cats) and 42 of 130 animals (32%; 21% of dogs, 53% of cats), respectively.

Diagnostic testing

An ECG was performed on every animal. The rhythms recorded included normal sinus rhythm (n=84; 49 dogs, 35 cats), sinus tachycardia (n=20; 12 dogs, 8 cats), atrial fibrillation (n=19; 12 dogs, 7 cats), ventricular premature depolarizations (n=8; 5 dogs, 3 cats), ventricular tachycardia (n=5; 3 dogs, 2 cats), atrial premature depolarizations (n=5 dogs), supraventricular tachycardia (n=3 dogs), and third degree atrioventricular block (n=1 dog). Systolic blood pressure was measured by an ultrasonic Doppler flow monitor in 82 animals (61 dogs, 21 cats). Median blood pressure in these 82 animals was 112 mm Hg (50–200 mm Hg). Median blood pressure for dogs was 112 mm Hg (65–200 mm Hg) while median blood pressure for cats was 110 mm Hg (50–180 mm Hg) (P=0.85). At the time of admission, 12 animals had a systolic blood pressure <90 mm Hg (9 dogs, 3 cats). However, the median lowest systolic blood pressure measured during hospitalization was 99 mm Hg (20–190 mm Hg), with 24 animals (18 dogs, 6 cats) having a systolic blood pressure <90 mm Hg at some point during hospitalization. Thoracic radiography was performed after admission to the hospital and radiographs were reviewed by a radiologist in 115 animals (75 dogs, 40 cats). Pulmonary edema was diagnosed in 67 dogs and 32 cats, while pleural effusion was noted in 13 dogs and 26 cats. Echocardiograms were performed by the cardiology service in 132 animals (84 dogs, 48 cats). Echocardiograms were performed by the emergency service only in an additional 5 animals and at the referring veterinarian only in 3 dogs. Five animals did not have an echocardiogram performed. The median ratio of the left atrial diameter to the aortic diameter was significantly higher in cats (1.90 [0.94–3.44]) compared with dogs (1.59 [0.73–3.08]) (P=0.001). The major underlying cardiac disease was determined for 136 animals. In dogs, the diseases represented were CVD (n=54), dilated cardiomyopathy (DCM; n=16), pericardial effusion (n=10), congenital disease (n=3: cor triatriatum dexter and pulmonic stenosis, n=1; ventricular septal defect, atrial septal defect, and tricuspid dysplasia, n=1, and congenital disease of undetermined cause, n=1), pulmonary hypertension (n=3), and 1 each of arrhythmogenic right ventricular cardiomyopathy and heartworm disease. In cats, the diseases represented were hypertrophic cardiomyopathy (n=23), DCM or cardiomyopathy with myocardial failure (n=12), unclassified cardiomyopathy (n=5), congenital disease (n=3; all mitral valve dysplasia), restrictive cardiomyopathy (n=4), and arrhythmogenic right ventricular cardiomyopathy (n=1).

Treatment

Treatments varied widely but common therapies included oxygen, diuretics, and centesis. Eighty-five of the animals (44 dogs, 41 cats) received oxygen therapy; median time in oxygen was 24 hours (1–105 h). Furosemide was administered to 106 (63 dogs, 43 cats) animals within the first 12 hours of hospitalization. For these animals, the median dosage in the first 12 hours of hospitalization was 2.67 mg/kg (0.78–9.00 mg/kg). The median furosemide dose in the first 12 hours was significantly higher in dogs (2.97 mg/kg [0.78–9.00 mg/kg]) compared with cats (2.00 mg/kg [0.87–7.47 mg/kg]) (P=0.003). Thoracocentesis was performed in 29 animals (5 dogs, 24 cats), while abdominocentesis was performed in 10 animals (9 dogs, 1 cat). Other medications used in the acute treatment of CHF included nitroglycerin (12 dogs, 4 cats), dopamine (1 dog, 2 cats), and dobutamine (1 dog). Four animals (2 dogs, 2 cats) were intubated and artificially ventilated during treatment of acute CHF.

Outcome

One hundred and sixteen animals (74 dogs, 42 cats) were discharged from the hospital. Most animals that were not discharged (n=29; 16 dogs, 13 cats) were euthanized but 4 dogs died during hospitalization. Survival was associated with ISACHC stage (P=0.03; most deaths were in animals classified as ISACHC stage 3b). There was no difference in survival between dogs and cats (P=0.39). There also was no association between survival and body condition score (P=0.95), gender (P=0.35), underlying disease (P=0.17), hyponatremia (at admission, P=0.60; during hospitalization, P=0.85), hypochloremia (at admission, P=0.19; during hospitalization, P=0.45), hypokalemia at admission (P=0.19), elevated BUN (at admission, P=0.30; during hospitalization, P=0.83), elevated creatinine (at admission, P=0.28; during hospitalization, P=0.56), hyperglycemia (P=0.36), elevated lactate (P=0.62), hypotension (at admission, P=0.75; during hospitalization, P=0.29), elevated liver enzymes (alanine aminotransferase [P=0.39], aspartate aminotransferase [P=0.64], alkaline phosphatase [P=0.21]), oxygen therapy (P=0.40), medications (P=0.13–0.56), or the presence of an arrhythmia (P=0.58). A greater proportion of animals with hypokalemia during hospitalization survived (91%) compared with those without hypokalemia (77%; P=0.03); this relationship was seen only in dogs (P=0.04) but not for cats (P=0.40). Dogs already receiving furosemide (P=0.02) or digoxin (P=0.04) at the time of admission and those that received furosemide during hospitalization (P=0.009) were more likely to have hypokalemia. For cats, but not for dogs, initial body temperature was lower for those cats that did not survive (P=0.02). For dogs, but not for cats, the presence of anemia at admission (P=0.002) and an older age (P=0.002) were associated with worse survival. For the animals that were discharged, median hospital time was 3 days (1–9 d). Median time in the intensive care unit was 3 days (<1–8 d). At the time of discharge, most animals (72 dogs, 42 cats of the total 145 animals) were receiving 1 or more cardiac medication. Medications included: furosemide (n=104), ACE inhibitor (n=96), pimobendan (n=64), digoxin (n=26), calcium-channel blocker (n=22), low–molecular-weight heparin (n=19), spironolactone (n=19), clopidogrel (n=18), β blocker (n=7), sildenafil (n=7), mexilitine (n=2), amiodarone (n=1), aspirin (n=1), and procainamide (n=1).

Discussion

This is a novel study of dogs and cats diagnosed with acute CHF and provides information that may be useful in characterizing the clinical presentation, management, and in-hospital outcomes of dogs and cats diagnosed with acute CHF. Most animals (80%) survived to discharge. Most previous veterinary studies reporting survival have been on specific subgroups of disease (eg, cats with hypertrophic cardiomyopathy, dogs with DCM) and the initial presentation of patients in such reports has not been well characterized. However, the survival rate in the current study is higher than 1 study of 59 dogs with CHF in which 56% survived.8 The study by Brady et al8 included only dogs and only those that had not yet received any cardiac medications so is not completely comparable. The largest database of a similar nature from humans (ADHERE) reported a mortality rate of <5%.3

Clinicopathologic abnormalities were common at the time of admission and became even more prevalent during hospitalization. Ninety percent of animals had a serum biochemistry profile performed at the time of admission and, at that time, most animals had abnormalities present. In 1 study, dogs with heart failure being treated with furosemide had significantly lower plasma potassium, magnesium, sodium, and chloride compared with healthy controls; however, that study was of chronic changes in heart failure compared with the acute situation evaluated in the current study.19 These changes also have been seen in other studies of chronic heart failure and can be influenced not only by medications but also by diet.20 Some of the abnormalities found in the current study (eg, electrolytes) are important to monitor as they could complicate the management of animals with CHF. This is particularly important as many of these became even more prevalent during hospitalization (eg, azotemia, hyponatremia, hypochloremia, and hypokalemia), and likely caused by diuretic use. It is also important to consider animals' concurrent diseases, such as renal disease or diabetes. However, other findings in the current study, such as elevated liver enzymes that are likely the result of low cardiac output or passive congestion, might not justify further investigation.

Hypotension at the time of admission (systolic blood pressure <90 mm Hg) was only found in 15% of animals in which it was measured, but this number nearly doubled (29%) during the course of hospitalization. Hypotension may be due to low cardiac output but also may be the result of cardiac medications. As hypotension can complicate the management of animals with CHF, serial measurement of blood pressure is recommended.

Hypotension and clinicopathologic abnormalities at the time of admission were not associated with mortality. This is in contrast to human studies in which hyponatremia, azotemia, and hypotension have been associated with mortality.2,3,7 This may be due to different underlying causes of CHF in dogs and cats compared with humans, to the option of euthanasia in dogs and cats (25/29 of the animals in this study that did not survive were euthanized), or to a smaller sample size (the ADHERE database, for example, included >100,000 humans). In the current study, the power for detecting a difference in survival based on the presence of hypotension at admission was only 11%. The positive association of development of hypokalemia during hospitalization with survival was most likely related to furosemide use. This may be related to these animals having owners willing to persist with treatment despite CHF and the resulting higher use of diuretics in these animals. Although it is difficult to know the exact cause of this relationship due to the possibility for euthanasia in veterinary patients, this finding may deserve further study.

In the current study, there was a predisposition for males, consistent with the underlying diseases (ie, CVD, cardiomyopathies) but no relationship between gender and survival. In similar human studies, results for gender are contradictory.3–6 In the ADHERE study, more women (62%) than men were admitted for acute decompensated CHF but in the EHFS I and EHFS II studies, 47% and 39% of patients were women, respectively.3–6 There was no association between gender and survival for either the ADHERE or EHFS II studies.21,22

From the ADHERE database, it was shown that body mass index was positively associated with survival and that obese patients had a higher rate of survival during hospitalization for CHF.23 This inverse relationship between weight or body mass index and survival time has now been demonstrated in multiple human studies and has been coined the obesity paradox.23–28 There are many possible mechanisms for the obesity paradox but it is likely due more to the lack of cachexia (ie, muscle loss associated with CHF) than to an actual benefit of obesity, given the adverse effects of cachexia in heart failure patients. The obesity paradox also has been demonstrated in dogs with chronic heart failure.29 However, in the current study, body condition score (recorded in 76% of animals) was not associated with survival. However, 44% of animals were considered to be below optimal body condition (ie, <5/9). The lack of relationship between body condition and survival may be the result of the short observation period during hospitalization, although the obesity paradox has been shown even for in-hospital survival in humans with acute decompensated heart failure.23 However, human studies of this nature have had a much larger sample size than the current one. In addition, the current study was limited by its retrospective nature in that an assessment of muscle loss or cachexia was not collected for each subject since body condition score only assesses fat stores. An assessment of lean body mass would help to determine whether effects of body condition seen in chronic cardiac disease also occur in acute CHF.

Contrary to human databases, ventilatory support and in-hospital intravenous inotropic therapy were used in a small proportion of the current study.3–6 These differing results may be explained by different underlying diseases, feasibility of noninvasive ventilatory support in humans, financial limitations for owners of companion animals, and the option for euthanasia in veterinary medicine. It also may be the result of clinician reluctance to use these treatments.

There are a number of limitations to this study. The most important limitation is the retrospective nature of the study that relies on the information in the medical record. Therefore, it was not possible to collect all the desired information for each dog and cat at the same time points, and treatments for each animal were not standardized. Treatments, both before and during hospitalization, were not standardized so the variability of drugs and other treatments may have affected the results. Another limitation of this retrospective study is the presence of CHF could not be confirmed at the time of admission by the investigators, as in a prospective study. Accurate inclusion of animals in the study was attempted by verifying the diagnosis of CHF using not only the diagnosis of CHF from the cardiology consultation report or discharge instructions, but also by reviewing physical examination, radiographic, and echocardiographic findings to ensure that they were consistent with a diagnosis of CHF. For example, thoracic radiographs were obtained in many animals shortly after hospital admission, but some animals had diagnostic radiographs obtained by the referring veterinarian and a diagnosis of CHF could be easily established by the attending emergency clinician based on these radiographs. However, as these radiographs were not available for review during data collection and had not been formally reviewed by a radiologist, these findings were not included. Despite careful and conservative review, this approach may have resulted in excluding some animals that had CHF and also in inadvertently including a small number of animals who did not truly have CHF. Not all animals included in the study were in their first episode of CHF. As each admission was considered a separate event, animals could be counted more than once. Nine animals were admitted >1 time, which may have influenced the results although this methodology also was used in the large human ADHERE study.2,3 Finally, this is a single-center study from a tertiary referral center so the results may not apply to all CHF patients.

Nonetheless, this study provides descriptive data that may be useful for clinicians when confronted with animals with acute CHF, a common problem for which animals are presented on an emergency basis to veterinary emergency services. CHF is associated with a variety of clinicopathologic abnormalities but with careful evaluation, monitoring, and treatment, a relatively high survival rate can be achieved. Larger prospective studies may help to determine predictors for mortality and optimal treatment regimens.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and Methods
  5. Results
  6. Footnotes
  7. References
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