2. A vessel approaching a blind bend in a river can sound one prolonged blast on the ships' whistle to alert any other vessels to its presence, if another vessel is nearby then they will respond with one prolonged blast on the ships' whistle.
Atrial fibrillation is often referred to as sick sinus syndrome because the sinoatrial (sinus) node in the right atrium controls the electrical impulses. The cause of atrial fibrillation is not always known. Conditions that can cause damage to the heart and lead to atrial fibrillation include: 1  high blood pressure.  congestive heart failure.
A-fib may be linked to conditions such as high blood pressure (hypertension), coronary artery disease, heart valve disease, heart failure, chronic lung disease or a clot in the lung (pulmonary embolism), among others. But in 10 percent of cases, A-fib is not associated with any other disease. Heart palpitations.