Cardiology Flashcards
What is flecainide and how it it intended to be used in horses?
Flecainide is, because of its sodium channel blocking properties, classified as a class IC antiarrhythmic drug. One of the prominent features of flecainide is slowing of the conduction velocity throughout the heart.
Flecainide may slow the atrial activation rate and eventually terminate AF by decreasing excitability, increasing the size and decreasing the number of re‐entrant circuits, primarily by widening the temporal excitable gap (the difference between AF cycle length [AFCL] and aERP during AF), by changing the appearance of the rotating wavefront or some combination of these effects.
A study was performed to evaluate the potential of flecainide to terminate acutely induced AF of short duration and to assess the properties of flecainide on AF duration and AF vulnerability in healthy horses.
10.1111/jvim.12496
How was flecainide evaluated as a treatment for acutely induced atrial fibrillation in healthy horses?
- Ability to terminate acute pacing-induced AF
- Drug-induced changes in atrial effective refractory period
- AF duration
- AF vulnerability
- Ventricular depolarization and repolarization times
10.1111/jvim.12496
Is flecainide viable as treatment for atrial fibrillation in horses?
Flecainide had clear antiarrhythmic effects terminating acute pacing‐induced AF of short duration (21 minutes) and resulted in decreased AF duration in healthy horses, but flecainide had no protective properties against immediate reinduction of AF and caused temporary prolongation in ventricular repolarization, which may be a potentially dangerous proarrhythmic effect.
10.1111/jvim.12496
What are two assays that can be used to detect myocardial damage?
Cardiac troponin I (cTnI) and troponin T (cTnT)
cTnT has only one manufacturer and thus preferred for use in humans.
10.1111/jvim.12530
When cTnI and cTnT were compared in detecting myocardial disease in horses, which test faired better?
Both cTnI and cTnT can distinguish healthy horses from horses with myocardial disease and have comparable diagnostic value. However, absolute cTnI and cTnT differences exist, which indicates that the same assay should be used for patient re‐evaluation.
10.1111/jvim.12530
What are some reasons for conversion of horses in atrial fibrillation?
Cardioversion is advised if horses have disproportionate tachycardia, QRS broadening or R‐on‐T phenomenon during exercise, because of the potential risk of these arrhythmias for exercise‐associated weakness, collapse, or even death.
10.1111/jvim.12606
What influences recurrence rate of atrial fibrillation?
Recurrence rate is independent of treatment modality but influenced by AF duration, atrial size and electrophysiological properties.
10.1111/jvim.12606
What are some potential prognostic factors when determining if atrial fibrillation will reoccur after conversion?
Signalment, AF history, cardiac comorbidities such as valvular regurgitation, method of treatment, and administration of drugs at or after cardioversion were included as potential prognostic factors. Study also looked at ECG changes that could be used to predict AF recurrence.
10.1111/jvim.12606
In a study looking at atrial fibrillation and horses that had been successfully converted, what were some risk factors for recurrence?
In horses with a first AF episode, previous unsuccessful treatment attempt and mitral regurgitation were identified as risk factors for recurrence in a multivariable model. When horses with recurrent AF were included, previous AF and low active left atrial fractional area change observed at 24 hours after cardioversion were risk factors for recurrence in a multivariable model.
10.1111/jvim.12606
How does brisket disease occur?
High altitude disease/brisket disease is initiated by hypoxia-induced pulmonary arteriolar narrowing. This leads to increases in resistance to blood flow, mean pulmonary arterial pressure and ultimately RHF
10.1111/jvim.13789
The occurrence of RHF in feedlot cattle has increased. A study was performed to try to determine the risk of RHF over time, to characterize some of the risk factors for RHF and to investigate how risk factors may affect the timing of RHF occurrence. What were the results?
RHF was reported in cattle at altitudes over 2,130 m, so a 2-fold increase in RHF over a 12 yr period in feedlots located at low to moderate elevations deserves attention. Half of all the cases occurred after 19 weeks, making death loss from RHF costly.
Factors predisposing cattle to alveolar hypoxia (primary risk factor for pulmonary vascular remodeling and hypertension) are hypobaric hypoxia, hyperventilation and respiratory disease.
Hypobaric hypoxia and its relationship with RHF and feedlot altitude was not assessed in this study.
BRD is a valid risk for RHF. Results show that cattle treated for BRD were 2–3 times more likely to die of RHF than cattle that were not treated for BRD.
Hypoventilation could be problematic in feedlot cattle.
First, ruminal engorgement after feeding could compress the lungs and, consequently, reduce effective alveolar ventilation; and second, feedlot cattle accumulate large amounts of body fat through the feeding period. The accumulation of fat in the abdomen and over the thorax could increase the mechanical work of breathing.
10.1111/jvim.13789
Prolonged exercise, as in endurance events, has been shown to cause changes in human cardiac function. List some of these.
Decreases in LV systolic and diastolic function (cardiac fatigue). Decreases in plasma volume and peripheral redistribution of blood, leading to tachycardia and reduced venous return.
10.1111/jvim.13982
Prolonged exercise in the form of endurance rides showed some cardiac function changes in horses. What were these changes and how significant were they?
Diastolic dysfunction characterized by small but significant decreases in early diastolic myocardial velocity and strain rate was observed in horses after the endurance rides. Ventricular filling was still reduced the next morning despite normalization of biochemical indicators of hydration status, indicating that the observed changes were not caused exclusively by reduced preload. Overall, the effects of prolonged exercise were small and the clinical relevance of these findings remains to be clarified.
10.1111/jvim.13982
How did blood cardiac troponin I and L-lactate concentrations contribute as prognostic indicators for a negative outcome in downer cow syndrome?
There was no association between LAC blood value and the outcome in downer cows. High troponinemia and high HR were associated with NO in DCS cases managed in a farm setting.
10.1111/jvim.14874
What is the approx recurrence rate of atrial fibrillation? What are some factors possibly associated with recurrence?
AF recurrence after treatment is common with an overall rate of recurrence up to 39% at 1 year after cardioversion. actors that might be associated with AF recurrence include structural changes to the atrial myocardium, atrial size and stretch, short atrial effective refractory period (AERP), and supraventricular ectopic foci.
10.1111/jvim.15055
