Distinctive atrioventricular type I heart block is diagnosed when the PQ interval is 0.30 s. or more. Prolongation of the PQ interval more than 0.50 s. is a very rare condition. Usually it is associated with a pseudo-pacemaker syndrome. The last one manifests itself with dizziness, syncope, general weakness, shortness of breath upon physical exertion, cough, seizures, cold sweat, a feeling of pulsation in the head, neck and abdomen, a headache, paroxysmal nocturnal dyspnea, swelling of the lower extremities, tachypnea and jugular venous pulsation. The P wave appears immediately after the previous QRS complex. Atrial contraction occurs at the moment when the ventricles don’t relax after the previous contraction; due to the fact that pressure in the ventricles at this moment is higher than in the atria, the tricuspid and mitral valves remains closed. During the atrial contraction, most of the blood is ejected not into the ventricles, but backward into the pulmonary veins from the left atrium and into the venae cavae from the right atrium. Also, an atrial kick is absent which results in a less ventricular filling. There is increased pressure in the atria leading to their distension and excessive secretion of the atrial natriuretic peptide.
A case report of the distinctive atrioventricular type I heart block associated with the pseudo-pacemaker syndrome is described. The patient suffered from a pre-syncope, short-term dizziness during the previous two days, tinnitus, general weakness, feeling of pulsation in the abdomen, neck, head, which interfered with his sleep. He developed these complaints after an infectious disease, which manifested as a runny nose and sore throat. In this patient, an extremely prolonged PQ interval up to 0.70 s. was observed. Also, episodes of Mobitz I and Mobitz type II atrioventricular block were detected. During the monitoring of patient state, the interval PQ was gradually shortening, and in 1 month it reached the normаl duration.
It can be assumed that in the case of distinctive atrioventricular type I heart block, a significant prolongation of the refractory period in the rapid pathways of the AV-node plays a key role in the pathogenesis of this condition.
According to the recommendations of the ACC/AHA (1998), for patients with distinctive atrioventricular type I heart block accompanied by the pseudo-pacemaker syndrome and documented alleviation of symptoms with temporary AV pacing, the pacemaker implantation should be considered (IIaB). The implantation of dual chamber pacemaker may reduce symptoms and lead to an improvement in the functional state of patients, in whom shortening of the interval between atrial and ventricular contractions improves hemodynamics. For asymptomatic patients with the PQ interval of ≥ 0.30 s, pacemaker is not recommended. The distinctive atrioventricular type I heart block in patients with pseudo-pacemaker syndrome is a rare condition and often remains undiagnosed. But it may have a benign course with a gradual normalization of the PQ interval. Indications for permanent pacemaker implantation should be reviewed as this block may be completely reversible. A permanent pacemaker may be used in the case of absence of positive dynamics in a shortening of the PQ interval.
Heart Block Caused by Ticagrelor Use in a Patient Who Underwent Adenosine Diastolic Fractional Reserve Assessment: A Case Report
