Synchronous diaphragmatic flutter (SDF) describes an involuntary, rhythmic contraction of the diaphragm muscle. The diaphragm is the primary muscle for breathing, located below the lungs. The term “synchronous” means these contractions often align with the heartbeat, creating a noticeable rhythm. This phenomenon is sometimes referred to as “thumps” in horses, where it is more commonly observed.
How Synchronous Diaphragmatic Flutter Occurs
The physiological basis of synchronous diaphragmatic flutter involves the phrenic nerve, which controls the diaphragm’s movement. This nerve runs through the chest cavity in close proximity to the heart. Electrical impulses from the heart’s rhythmic contractions can inadvertently stimulate the phrenic nerve.
This stimulation causes the diaphragm to contract in sync with each heartbeat, rather than with the normal breathing cycle. These additional, synchronized contractions create the characteristic flutter. This abnormal excitation of the phrenic nerve can also arise from irritation of the diaphragm itself.
Factors Contributing to Synchronous Diaphragmatic Flutter
Electrolyte imbalances are a common underlying cause, particularly deficits in calcium, potassium, magnesium, and chloride. For instance, a decrease in plasma calcium (hypocalcemia) or potassium (hypokalemia) can sensitize the phrenic nerve, making it more susceptible to stimulation by the adjacent heart’s electrical activity. Severe dehydration can also contribute to these electrolyte disturbances.
Gastrointestinal issues, such as colic or impaction, can lead to fluid and electrolyte losses, exacerbating the problem. SDF is notably observed in horses, especially after strenuous exercise or during severe diarrhea. Certain medications or prolonged surgical procedures with anesthesia may also play a role in altering electrolyte balance or nerve sensitivity.
Identifying the Signs of Synchronous Diaphragmatic Flutter
The most characteristic symptom of synchronous diaphragmatic flutter is a visible twitching or spasm in the flank area, which is synchronized with the animal’s heartbeat. This involuntary movement can be seen as a rhythmic “thump” or pulsation in the upper abdomen or chest region. These movements are not associated with the breathing cycle but rather directly correspond to each beat of the heart.
Observers may also hear a distinct “thump” sound, which can often be palpated (felt) over the thorax or flanks. The intensity of these movements can vary, from subtle twitches to more pronounced, repetitive contractions of the diaphragm. While generally not painful, prolonged bouts of these contractions can cause discomfort or even pain in some cases, potentially accompanied by symptoms like breathing difficulties, chest pain, or abdominal discomfort.
Approaches to Diagnosis and Management
Diagnosing synchronous diaphragmatic flutter typically begins with a physical examination, where the characteristic synchronized diaphragmatic contractions are observed and felt. A veterinarian or medical professional will listen to the heart and simultaneously assess the muscle contractions in the flank or abdominal area to confirm their synchronization with the heartbeat. Blood tests are also performed to identify any underlying biochemical abnormalities, such as imbalances in electrolytes like calcium, potassium, sodium, chloride, and magnesium. Dehydration levels and other metabolic indicators like blood lactate may also be assessed.
Management of SDF primarily focuses on correcting the underlying cause. This often involves replenishing depleted electrolytes and addressing dehydration through fluid therapy, which may be administered intravenously in severe cases. For instance, providing isotonic or slightly hypertonic fluids supplemented with calcium, potassium, and glucose can rapidly improve the condition. If gastrointestinal issues are contributing, they must also be treated. The prognosis for synchronous diaphragmatic flutter is generally favorable, with symptoms resolving once the primary condition, particularly electrolyte imbalances, is effectively treated.