Extrasystole

An extrasystole is an additional, premature heartbeat that falls outside the normal rhythm. Such skipped beats occur in dogs – sometimes in completely healthy animals, sometimes in connection with a genuine heart disease. This makes them so tricky: they can be harmless, but they can also indicate a serious heart problem that needs to be treated.

What is an extrasystole?

Simplified: the heart beats once too early. This is triggered by faulty electrical activity – a small signal that does not fit into the regular rhythm pattern. Depending on where this signal originates, two types are distinguished:

• Supraventricular extrasystole: The origin lies in the atria. Such extrasystoles are usually less dangerous and often remain without consequences.
• Ventricular extrasystole: It originates in the ventricles. This is the more serious variant – especially when it becomes frequent.

In both cases, the normal heart rhythm is briefly interrupted. This can be a one-off occurrence or repeat itself repeatedly.

Causes of extrasystoles in dogs

The triggers are diverse. The following factors are most commonly involved:

1. Heart diseases: Cardiomyopathy, heart failure and valvular heart disease disrupt the electrical order in the heart – and this precisely opens the door to irregular beats.
2. Electrolyte imbalances: Too little or too much potassium, calcium or sodium throws the electrical signals of the heart muscle out of sync. Such imbalances are an underestimated trigger.
3. Stress and excitement: Strong emotional arousal activates the nervous system – and sensitive dogs can consequently develop temporary extrasystoles. This is not uncommon to observe at veterinary visits.
4. Medications: Some active ingredients – including diuretics or certain heart medications – can shift the electrical conductivity of the heart and thereby favour extrasystoles.
5. Toxins: Poisons and heavy metals that attack the heart muscle or nervous system also count among the possible causes. Poisonings are sometimes only discovered via arrhythmias.
6. Anaemia: In blood deficiency, oxygen levels in the tissue drop. The heart attempts to compensate by beating faster and more forcefully – which increases the risk of extrasystoles.
7. Hormonal disorders: Hyperthyroidism (overactive thyroid) or Cushing’s syndrome can disrupt the entire metabolism and thus also the heart rhythm.

Symptoms of an extrasystole in dogs

To be honest: many dogs show no signs at all. Extrasystoles are often discovered by chance during a routine check-up or an ECG – the dog itself appears completely fit. If something does stand out, it is usually these signs:

• Irregular heartbeat: In more severe cases, you can feel a strange stumbling of the heartbeat when palpating the chest.
• Weakness or fainting: Frequent or pronounced extrasystoles can cause the dog to suddenly collapse or wobble – because blood flow to the brain briefly stops.
• Shortness of breath: Affected dogs tire more quickly than usual and may develop breathing problems.
• Lethargy: A generally reduced level of activity, without any other obvious explanation, can indicate a disturbed heart rhythm.
• Coughing: If heart failure is present as the underlying condition, coughing often occurs too – a symptom that many initially mistake for respiratory diseases.

Diagnosis of Extrasystoles

No single test is sufficient – diagnosis usually involves several steps:

1. Auscultation: First, the vet listens to the heart with a stethoscope. Extrasystoles stand out as additional heart sounds or irregular rhythms – an experienced ear recognises this quickly.
2. Electrocardiogram (ECG): The ECG is the decisive tool. It records the electrical activity of the heart and shows exactly whether and when premature beats occur. Furthermore, it can be determined from this whether they are supraventricular or ventricular extrasystoles.
3. Blood tests: Blood tests help to detect electrolyte imbalances, anaemia or hormonal disorders such as hyperthyroidism – all potential triggers.
4. Echocardiography (cardiac ultrasound): The cardiac ultrasound makes structural changes visible – thickened walls, enlarged chambers or other abnormalities that make the heart susceptible to arrhythmias.
5. Long-term ECG (Holter monitoring): If there is suspicion of frequent or only occasionally occurring extrasystoles, the dog wears a Holter monitor. The device records heart activity over 24 hours or longer – thus capturing events that would simply not be visible during a short practice examination.

Treatment of Extrasystoles in Dogs

How much intervention is required depends on the cause and severity. Mild cases without symptoms often require no therapy – regular check-ups are then sufficient. In more severe courses or with a proven underlying disease, various approaches are used:

Medications:

• Antiarrhythmics such as Lidocaine or Sotalol can keep the irregular beats under control. They directly affect the electrical activity of the heart and reduce the frequency of skipped beats.
• If a heart disease is behind it, ACE inhibitors or diuretics are often added additionally – to relieve the heart and alleviate symptoms.

Electrolyte therapy:

• In proven electrolyte imbalances, targeted administration of potassium, calcium or magnesium can stabilise the heart rhythm again – sometimes with surprisingly rapid effect.

Treatment of the underlying condition:

• If thyroid problems, heart failure or other diseases are the actual cause, therapy is directed against these – and not just against the symptom of extrasystole. Often the heart rhythm normalises as soon as the underlying problem is treated.

Monitoring:

• In asymptomatic dogs, it is often sufficient to keep an eye on heart function. The vet carries out regular ECGs or other tests for this purpose – not to treat unnecessarily, but to notice in good time if something changes.

Prognosis

The outlook depends heavily on what lies behind the extrasystoles. Healthy dogs with occasional outliers and no other heart disease have a good prognosis – the disturbance usually remains insignificant. It looks different for dogs with existing heart diseases or frequent ventricular extrasystoles: here the prognosis can be significantly less favourable, and long-term monitoring as well as consistent treatment are then not an option, but mandatory.