A new veterinary study has found that dogs suffering from brachycephalic obstructive airway syndrome (BOAS) may experience changes in the way their heart is regulated, adding to growing evidence that the condition affects far more than breathing alone.
Researchers from the Federal University of Paraná in Brazil monitored 46 dogs over a 24-hour period, comparing healthy non-brachycephalic dogs with flat-faced breeds both with and without BOAS. The findings, published in the Journal of Veterinary Internal Medicine, suggest that dogs with moderate to severe BOAS show significant differences in heart rate variability – a measure of how the nervous system controls the heart.
What is BOAS?
Brachycephalic obstructive airway syndrome is a condition caused by the shortened skull shape seen in breeds such as French Bulldogs, Pugs, English Bulldogs, Boston Terriers and Shih Tzus.
Many affected dogs have narrowed nostrils, elongated soft palates and other abnormalities that make breathing more difficult. Symptoms can include noisy breathing, snoring, exercise intolerance, overheating and, in severe cases, collapse.
While owners often recognise the breathing problems, scientists have increasingly been investigating whether the condition also affects other parts of the body.
What did the study find?
The researchers fitted participating dogs with 24-hour heart monitors to assess their heart rhythm while awake and asleep.
Dogs diagnosed with moderate to severe BOAS showed:
- Higher heart rate variability, suggesting altered nervous system control of the heart.
- More frequent and longer pauses between heartbeats, known as sinus pauses.
- Stronger signs of increased parasympathetic (vagal) activity compared with healthy dogs.
Interestingly, all dogs experienced increased parasympathetic activity while sleeping, which is a normal physiological response. However, the differences between healthy dogs and those with BOAS were most noticeable when the animals were awake.
According to the researchers, this suggests that the chronic effort required to breathe and repeated episodes of reduced oxygen levels during the day may have a greater impact on the cardiovascular system than previously recognised.
Does this mean BOAS causes heart disease?
Not necessarily.
The researchers are careful to point out that the changes they observed reflect how the nervous system regulates the heart, rather than evidence that the dogs had heart disease.
In fact, all of the dogs enrolled in the study underwent cardiac examinations before taking part, and dogs with existing heart disease or significant rhythm disorders were excluded.
Instead, the findings suggest that breathing problems associated with BOAS may place additional strain on the body’s autonomic nervous system, which controls functions such as heart rate, breathing and blood pressure.
More evidence that BOAS affects the whole body
BOAS has long been viewed primarily as an airway disorder, but research over recent years has linked it to wider health concerns including overheating, exercise intolerance, gastrointestinal problems, sleep disruption and reduced quality of life.
This latest study adds to that growing body of evidence by suggesting that the condition may also influence the body’s cardiovascular regulation.
The researchers believe the findings reinforce the importance of recognising BOAS as a systemic welfare issue rather than simply a cosmetic consequence of having a flat face.
What does this mean for owners?
The study does not suggest that every flat-faced dog has heart problems, nor does it mean owners should panic.
However, it highlights why persistent signs such as noisy breathing, excessive panting, poor exercise tolerance or disturbed sleep should not be dismissed as “normal for the breed.”
Veterinary assessment is recommended for dogs showing symptoms of BOAS, as treatment, including weight management and, in some cases, corrective airway surgery, can significantly improve quality of life.
As with all scientific research, the authors note that larger studies will be needed to confirm their findings and better understand the long-term effects of BOAS on the heart.
Read the full study
The complete peer-reviewed research paper is available in the Journal of Veterinary Internal Medicine.
