N. Schechtmann

Detection and characterization of acute myocardial infarction in man with use of gated magnetic resonance.

To evaluate the capability of magnetic resonance imaging (MRI) in the detection and characterization of alterations in signal intensity and T2 relaxation time in acutely infarcted relative to normal myocardium 16 adult patients and normal volunteers were studied by electrocardiographically gated proton MRI. The seven volunteers were entirely asymptomatic and had no history of cardiovascular abnormality. The nine patients had each suffered an acute myocardial infarction within 5 to 12 days before the MRI studies. The diagnosis in each patient was confirmed by electrocardiographic (ECG) criteria and elevated levels of fractionated creatine kinase (CK) isoenzymes. Electrocardiographically gated MRI was performed with a superconducting system operating at 0.35 tesla. MRI demonstrated infarcted myocardium as a region of high signal intensity relative to that of adjacent normal myocardium; regions of high intensity corresponded anatomically to the site of infarction as defined by the ECG changes. The mean percent difference between normal and infarcted myocardium was substantially greater on 56 msec images (70.2 +/- 21.3%) compared with 28 msec images (27.1 +/- 13.6%). Region of interest analysis revealed that infarcted myocardium had a significantly (p less than .01) prolonged T2 relaxation time (mean T2 = 80.9 msec) relative to that in normal myocardium (mean T2 = 42.3 msec) and relative to the mean T2 of left ventricular myocardium in the volunteers (mean T2 = 42.4 msec). An additional finding for each patient with myocardial infarction was a high intraluminal flow signal on 56 msec images, but this was also observed in normal subjects and is therefore a nonspecific finding.(ABSTRACT TRUNCATED AT 250 WORDS)

The scintigraphic characteristics of ventricular pre-excitation through Mahaim fibers with the use of phase analysis.

The phase image pattern of blood pool scintigrams was blindly assessed in 11 patients exhibiting conduction through Mahaim pathways, including 6 nodoventricular and 5 fasciculoventricular. These patterns were compared with the phase image findings in normal subjects, patients with left and right bundle branch block in the absence of pre-excitation and patients with pre-excitation through atrioventricular (AV) connections. In all patients with a Mahaim pathway, the site of earliest phase angle was septal or paraseptal. Phase progression was asymmetric and the pre-excited ventricle demonstrated the earliest mean ventricular phase angle in 10 of 11 patients. This pattern, and the associated ventricular phase difference, appeared to vary from that in normal subjects and in those with a septal AV connection, in whom phase progression is generally symmetric. Scintigraphic phase analysis provided localizing information and presented patterns consistent with Mahaim pathways. Although not able to differentiate among Mahaim pathway subtypes, these phase patterns differed from those in normal subjects, those with right and left lateral free wall pathways and most patients with a septal AV pathway. However, the phase pattern of patients with a Mahaim pathway may not differ from that of patients with a septal AV connection displaying an asymmetric pattern of phase progression, or those with left and right bundle branch block in the absence of pre-excitation. Objective, yet imperfect phase measurements supported these differences. Such image findings may complement the often complex electrophysiologic evaluation of patients presenting with pre-excitation.

The effects of coronary angioplasty and reperfusion on distribution of myocardial flow.

To assess the effects of angioplasty (PTCA) and intracoronary streptokinase (ICSK) on relative myocardial perfusion, we administered 99mTc-macroaggregated albumin (MAA) to the uninvolved coronary artery before successful PTCA in 33 patients and before successful infusion of ICSK in eight patients and of 111In-MAA into the same vessel after the intervention. In 10 patients who underwent PTCA, MAA was injected into the involved, instrumented coronary artery. Computer-processed images were acquired in registry and compared. Similar scintigraphic studies were performed in six control patients and in 11 in whom planned interventions were not performed or were unsuccessful. Distribution of MAA was also compared with angiographic results and with the distribution of 201Tl on images obtained in patients at rest or on redistribution images obtained before and soon after intervention in 22 patients. In control patients and those studied after aborted or unsuccessful intervention, scintigraphic results showed excellent correlation with the angiographic anatomy and were without serial change. When MAA was injected into the uninvolved vessel, the scintigram revealed evidence of collateral perfusion with retraction of the perfusion zone from that of the involved coronary in 19 of 33 patients undergoing PTCA and in three of eight of those receiving ICSK. When MAA was injected into the involved artery, a relative increase in perfusion was seen in eight of 10 patients after PTCA. Although 30 patients demonstrated scintigraphic evidence of collateral vessels, only 10 patients had angiographic evidence of collateral circulation before intervention. The distribution of 201Tl demonstrated little change in its global pattern and regions previously supplied by collaterals were generally well perfused after intervention. Coronary collateral perfusion may be inapparent angiographically and regress rapidly after angioplasty or reperfusion. Native perfusion is generally and quickly restored after successful PTCA or ICSK infusion, which obviates the need for collaterals. After intervention, the distribution of total perfusion may not change, but its regional source may demonstrate beneficial alterations, shifting from collateral to native circulation.

Localization of Ventricular Tachycardia Exit Site and Subsequent Contraction Sequence and Functional Effects With Bedside Radionuclide Angiography

OBJECTIVES In an effort to better understand the clinical effects of ventricular tachycardia (VT), we sought to characterize function and conduction during VT in patients. BACKGROUND The image evaluation of VT has been limited by the lack of technical tools and its often-dramatic hemodynamic effect. Objective bedside imaging of VT-induced changes in contraction pattern, synchrony, and volumes has never been performed but could aid in the understanding of rhythm tolerance. METHODS Equilibrium radionuclide angiography (ERNA) with phase analysis was performed during the course of 32 VT rhythms. Left ventricular ejection fraction, wall motion, synchrony, relative volumes, and exit sites were compared in 13 patients tolerant to VT (Group I) and 9 intolerant to VT (Group II). RESULTS The ERNA VT exit site agreed with the results of electrocardiogram in 26 of 32 (81%) cases and with electrophysiologic study in 16 of 19 (84%) cases (both p < 0.05). A greater rate (157 vs. 130, p < 0.0001) accompanied VT intolerance, but the exit site in 4 patients with multiple VT patterns also appeared important to tolerance. Left ventricular ejection fraction, similar in both groups in sinus rhythm, decreased with VT in Groups I (28 to 19) and II (31 to 15), both p<0.03, with a greater relative decrease in LV ejection fraction, LV stroke volume (65% vs. 45%, p < 0.01), cardiac output (30% vs. 2%), and LV end-diastolic volume (36% vs. 27%, both p < 0.001), in Group II. The standard deviation of LV phase angle (Ø) was the only parameter which differed between Groups I and II (35 vs. 45, p < 0.01) in sinus rhythm. With VT, wall motion deteriorated generally, but with greater standard deviation LVØ, p < 0.05, and dyssynchrony in Group II. Ventricular tachycardia induced 14 functional aneurysms, often adjacent to VT exit sites. CONCLUSIONS A challenging bedside imaging protocol evaluated VT-induced changes. We found that the use of ERNA demonstrated function, synchrony, and volume differences between tolerant and intolerant VT rhythms, delineated the contraction pattern, and localized exit sites.