CONTRACTILE FUNCTION OF THE LEFT ATRIUM AND PULMONARY VEINS BEFORE AND FOLLOWING THEIR ANTRUM ISOLATION

To study contractile function of the left atrium (LA) and pulmonary veins (PV) before and immediately after the PV antrum isolation, transthoracic and transesophageal echocardiography was performed in 17 patients (10 men and 7 women) aged 57.4±8.3 years. Five patients suffered from paroxysmal atrial fibrillation (AF) and 12 patients had persistent AF. The arrhythmic history was 25.2±8.1 months. The arrhythmia was considered idiopathic in 12 patients and a sign of post-infarction or post-myocarditic cardiosclerosis in 5 ones. All patients before the PV antrum isolation had the sinus rhythm; in none of them, signs of the LA stunning were revealed during transthoracic echocardiography. Multispiral computed tomography (MSCT) of the heart was performed using a 64 slice device, Somatom Sensation 6 (Siemens). 100 ml of contrast media containing iodine in a concentration of 350 mg/ml were administered as intravenous bolus injections into the cubital vein with the aid of automated syringe injector. The images recorded were analyzed using the Leonardo multi-modal workstation (Siemens). Transthoracic echocardiography was carried out using ultrasound scanner Aloka SSD 500 ProSound. Alterations of transmitral flow typical for the left ventricle (LV) diastolic dysfunction in most patients were revealed after the PV antrum isolation. The normal type of transmitral flow reported at baseline transformed into the pseudo-normal type in 17% of cases (2 cases of 12) and into the restrictive type in 10 cases (83%). The baseline diastolic dysfunction of hypertrophic type upon the procedure termination was followed by restrictive type of transmitral flow in all 5 cases. However, end diastolic LV pressure measured invasively after the PV antrum isolation did not change (8.2±2.2 mm Hg and 8.3±2.2 mm Hg, respectively). Thus, the transmitral flow dynamics were related to alterations of contractile function of the left atrium itself rather than the LV diastolic dysfunction. The assessment of circulation in PA showed that their isolation led to a decreased peak velocity of both anterograde and retrograde phases. Thus, after the PV antrum isolation, deterioration of the LA reservoir function occurs, without alterations in the left auricle contractile function. The contractile function of LA and PV muscular muffs was assessed with the aid of transesophageal echocardiography and continuous direct manometry in the cavities of LA, LV, as well as inside a balloon inflated at the level of PV muffs. The soft elastic balloon was inflated by a contrast medium until complete occlusion of the corresponding PV, without stretching its muscular muffs. All measurements were conducted both before and after the PV antrum isolation. Peaks of balloon pressure revealed did not absolutely coincide with E and A peaks relevant to the transmitral flow. During the LA passive relaxation, LV muscular muffs were also contracting. Elevated LA and balloon pressure was achieved also during active atrial systole, therefore, the PV muff was also contracting. After the PV antrum isolation, the balloon pressure curve dampened that probably gave evidence of the relief of active contractile function of PV mechanic muffs. During multi-spiral computed tomography, the PV diameter fluctuation also decreased significantly. Thus, after the LV antrum isolation, deterioration of the LA reservoir function takes place, without changes in the left auricle contractility. Hemodynamic alterations in PV due to an impaired contractility of their muffs are main mechanisms of this effect.

atrial fibrillation, pulmonary veins, left computed tomography, direct manometry

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