Regional Akinesia Research Articles

Radionuclide Phase Imaging of Ventricular Tachycardia

The emptying sequence of ventricular blood pool was studied by scintigraphic regional phase mapping in 10 patients with monomorphic and sustained ventricular tachycardia (VT) and compared to an electrophysiological study in order to assess the scintigraphic accuracy for the noninvasive localization of abnormal site of activation. All patients underwent both phase imaging and electrical mapping studies. There were 6 coronary artery disease patients, 3 patients with arrhythmogenic right ventricular disease and 1 patient with dilatative cardiomyopathy. Phase image studies were performed by first harmonic Fourier analysis of radionuclide angiography either during sinus rhythm or during spontaneous or catheter-induced VT. Eleven morphologically distinct VTs with a heart rate ranging from 145 to 260 beats min^-1 (mean 173 ± 32 beats min^-1) were imaged. Endocardial catheter mapping was accomplished in 9 different VT morphologies. Three patients also had epicardial intraoperative mapping. The site of origin of VT by a scintigraphic method was defined as the area of earliest regional contraction on the biventricular scintigram. By separating the right ventricle into 5 segments and the left ventricle into 7 segments, with multiple view cardiac imaging, a close correspondence between the site of origin determined by electrophysiological study and the region of earliest emptying of radioactivity was observed in 7 of 9 (77%) VTs. In 2 patients the extension of regional akinesia during VT prevented us from an accurate mapping of the regional time sequence of contraction. Scintigraphic phase mapping has inherent limitations due to wall motion dependency and relatively low resolution power but it is feasible in selected patients with monomorphic, inducible and long-sustained VT in whom adequate time for data collection is provided. In this subset of patients the site of origin of VT could be localized on a 'segmental' basis with close correspondence to electrophysiological mapping studies.

Recruitment of inotropic reserve in "stunned" myocardium by the cardiotonic agent AR-L 57.

Contractile dysfunction of reversibly injured, reperfused myocardium can be enhanced by inotropic interventions. A decrease in the Ca-sensitivity of contractile proteins with slow recovery during reperfusion has been suggested as a potential mechanism underlying this postischemic dysfunction. We therefore tested the effects of the cardiotonic agent AR-L 57 (1 mg/kg i.v.) in six anesthetized, vagotomized dogs during constant atrial pacing at 192 +/- 6 beats/min. Before ischemia, AR-L 57 increased left ventricular pressure from 131 +/- 22 to 138 +/- 21 mm Hg and maximum dP/dt from 3,022 +/- 1,427 to 4,337 +/- 2,608 mm Hg/s. Mean systolic thickening velocity of the posterior myocardium was increased from 8.9 +/- 1.1 to 11.7 +/- 1.1 mm/s. After release of a 15 min LCX-occlusion which caused complete regional akinesia, baseline function in the posterior myocardium was severely depressed and only gradually returned towards control values over 8 h of reperfusion. AR-L 57 increased systolic thickening velocity at 10 min, 4 and 8 h reperfusion to a similar extent as before ischemia. With reference to a purported Ca-sensitizing mechanism underlying the positive inotropic action of AR-L 57, our data suggest no change in the Ca-sensitivity of reperfused myocardium.

Morphology of ventricular premature beats as an aid in the electrocardiographic diagnosis of myocardial infarction

To determine whether morphologic analysis of ventricular premature beats (VPBs) can aid in the electrocardiographic diagnosis of myocardial infarction (MI), 12-lead electrocardiograms were evaluated in 760 consecutive patients who underwent cardiac catheterization, and 2-minute multiple-lead rhythm strips were evaluated in 515 of these patients. VPBs occurred in 58 patients; 21 had prior MI diagnosed by regional akinesia or dyskinesia on left ventricular cineangiography. Standard criteria were used to diagnose prior MI from the sinus beats of the electrocardiogram. Infarction was diagnosed from the morphology of a VPB when it had a QR or QRS pattern with Q wave ≥ 0.04 second. Morphologic analysis of VPBs had a low sensitivity (29%) but high specificity (97%) and high predictive value (86%) for the diagnosis of Ml. Sinus beats diagnosed Ml with higher sensitivity (52%, and 69% if patients with left bundle branch block and left ventricular hypertrophy were excluded from analysis) than VPB morphologic analysis (p < 0.05), but with similar specificity (97%) and predictive value (92%). Two patients with angiographic Ml had no Ml according to standard electrocardiographic criteria, but did have an Ml manifest by VPB morphologic analysis. Despite low sensitivity, analysis of the morphology of VPBs may be useful for the diagnosis of Ml when the morphology of sinus beats is not diagnostic. Therefore, VPB analysis is complementary to the standard electrocardiographic diagnosis of MI.

Left bundle branch block: Angiographic segmental wall motion abnormalities

Ventricular wall motion as studied with contrast ventriculography has been judged normal in the few previously reported cases of patients with left bundle branch block who have neither coronary artery disease nor diffuse cardiomyopathy. However, recent echocardiographic studies have demonstrated a high frequency of segmental asynergy of the septal wall in such patients. In this study left ventricular wall motion was analyzed in 15 patients with left bundle branch block and without significant coronary artery disease or diffuse cardiomyopathy. Biplane cineangiograms from these patients were compared with those from 100 consecutive patients with normal intraventricular conduction and without coronary artery disease or cardiomyopathy using two techniques: qualitative visual inspection and a computer-assisted quantitative method. By qualitative review, 6 of 15 patients with left bundle branch block had regional akinesia or dyskinesia as compared with none of 100 patients with normal intraventricular conduction (chi square = 42.3; P < 0.001). By quantitative review, 10 of 12 patients with left bundle branch block had abnormal wall motion along at least one hemiaxis. It is concluded that angiographic regional wall motion abnormalities are common in patients with left bundle branch block, even in the absence of coronary artery disease or diffuse cardiomyopathy. The abnormalities may result from the abnormal sequence of ventricular activation rather than from myocardial fibrosis.

Coronary collateral circulation and distal coronary runoff: the key factors in pre-serving myocardial contractility in patients with coronary artery disease.

CORONARY COLLATERAL CIRCULATION AND DISTAL CORONARY RUNOFF: THE KEY FACTORS IN PRESERVING MYOCARDIAL CONTRACTILITY IN PATIENTS WITH CORONARY ARTERY DISEASEDAVID C. LEVIN, M.D., THOMAS A. SOS, M.D., JACK G. LEE, M.D. and HAROLD A. BALTAXE, M.D.Audio Available | Share