Although less common, a large number of heartworms can lead to a sudden obstruction of blood flow through the heart and lungs. (tampabayvets.net)
The two separate sounds are the result of multiple valves closing as blood flows through the heart. (mykidhaspaws.org)
The effects of the heartworm are to physically block the normal blood flow through your heart and to damage the lining of the heart muscle inside the right chamber. (norwalkanimalhospital.com)