Hi, Breathlessness and a high heart rate can be caused by a variety of factors in individuals with arrhythmia, or an irregular heartbeat. Here are some potential explanations: * Arrhythmia: The arrhythmia itself may be causing breathlessness and a high heart rate. Arrhythmias can cause the heart to beat too fast, too slow, or irregularly, which can lead to a variety of symptoms. * Medication side effects: Some medications used to treat arrhythmias can cause side effects such as breathlessness, dizziness, and a rapid heartbeat. * Cardiac event: The symptoms your husband experienced could be a sign of a cardiac event, such as angina or a heart attack. It is important to seek medical attention immediately if you suspect this may be the case. * Physical exertion: The physical activity of washing windows and bending down to pick up the ladder may have caused an increase in heart rate and breathlessness. * Dehydration or electrolyte imbalance: Dehydration or an electrolyte imbalance can lead to symptoms such as dizziness, rapid heart rate, and fatigue. It is important to have your husband evaluated by his healthcare provider, especially if these symptoms persist or worsen. They may recommend an EKG or other tests to evaluate his heart function and determine if any adjustments are needed to his medication regimen. In the meantime, it may be helpful to avoid any strenuous physical activity and ensure he is staying hydrated. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Priyanka, General & Family Physician