Prediction of reversibility of chronic ischemic myocardial dysfunction: comparative accuracy of rest early and delayed redistribution thallium-201 tomography and low-dose dobutamine echo-cardiography

The current study sought to directly compare the diagnostic accuracy of rest early- and delayed thallium single-photon emission computed tomography and low-dose dobutamine echocardiography for prediction of contractile recovery of hibernating myocardium after coronary revascularization.Thallium SPECT and dobutamine echocardiography permit differentiation of viable from non-viable myocardium. However, few studies have directly compared their accuracy in the same patients.Twenty eight consecutive patients [22 men and 6 women, aged 39 to 71 years; mean 58 +/- 8 years] with old anterior myocardial infarction, and rest ischemic segmental ventricular dysfunction [potentially hibernating myocardium] underwent rest early-and delayed redistribution thallium SPECT and low-dose dobutamine echocardiography before coronary re-vascularization. Recovery of segmental and global dysfunction was assessed by echocardiography 1l +/- 2 weeks after re-vascularization. For analysis, the left ventricle was divided into 16 segments and regional wall motion was graded semi-quantitatively [I = normal, 2 = hypokinetic, 3 = akinetic, and 4 = dyskinetic]. Percent thallium activities were quantified, using circumferential profiles as early [I0-minute] and delayed [l7-hour] and expressed as a percentage of maximal activity in each projection, using the same 16-segment model. Before revascularization, 82 segments were grouped as normal [normal segment function and coronary stenosis <70%, group I]; in the remaining segments with coronary stenosis >/= 70%, 176 segments had normal function [group II], and 190 segments showed rest dysfunction [group lll]. Early and delayed thallium-20I regional percent activities did not differ in group I and in group II but were significantly less in group III. Segments with improved wall motion during dobutamine infusion had more significant early and delayed thallium-20I uptakes than unresponsive segments. Of the 190 initially dysfunctional segments, 117 segments [62%] resumed functional recovery at follow-up after revascularization. The diagnostic accuracy of the two techniques was studied both for global function [individual patient] and for individual segmental function. Global functional analysis showed that left ventricular ejection fraction rose by >/= 9% in 15 patients [59%] and rose significantly from a mean value of 38 +/- 8 to 46 +/- I0 after revascularization. Early and delayed thallium SPECT and low-dose dobutamine echocardiography had sensitivities of 75%, 80% and 90%; respectively, and specificities of 45%, 77% and 82%, respectively, for prediction of post-revascularization global functional recovery. Thus, only early thallium-20I SPECT was significantly less specific [P < 0.001] than both delayed thallium-20I SPECT and dobutamine echocardiography in prediction of unrecovered global left ventricular function after revascularization. Segmental functional analysis showed that all modalities had comparable sensitivities 78%, 87% and 87%; respectively [P > 0.05]. Meanwhile, both delayed thallium-20I SPECT and dobutamine echocardiography were significantly highly specific [84% and 79%; respectively, P > 0.05] than early thallium-20I SPECT [49%, P < 0.001] in prediction of unrecovered segmental wall function after revascularization. The predictive accuracy of the three modalities was 67%, 86% and 84%, respectively.The current study indicated that both delayed thallium-201 SPECT and low-dose dobutamine echocardiography had comparable sensitivity, specificity and accuracy in prediction of hibernating myocardium. Meanwhile, early thallium-20I was equally sensitive by significantly less specific and accurate than the earlier modalities for prediction of hibernating myocardium

Adenosine bedside test for diagnosis of dual AV-Nodal physiology in patients with supraventricular tachycardia

AV-nodal reenterent tachycardia [AVNRT] is one of the most common forms of supraventricular tachycardias [SVTs]. Intravenous adenosine can terminate this arrhythmia and unmask the underlying mechanisms. Utilization of adenosine as a bedside test for diagnosis of dual AV-nodal physiology and subsequently the AVNRT The current study included 20 patients with documented SVTs and were referred for diagnostic electrophysiologic study [EPS] and radiofrequency ablation. Twelve were women and eight were men with a mean age of 33 +/- 10.6 years, range [12 to 47]. Inclusion criteria included: 1] documented SVTs either by surface ECG or 24-hour Holter monitoring, 2] no history of previous EPS with or without ablation, and 3] all patients were off anti-arrythmic medications or drugs that interfer with adenosine actions. Patients with surface ECGs that showed signs of antegrade conducting pathway were excluded. Adenosine test. Adenosine was rapidly injected via one femoral vein sheath. Adenosine was administered at increasing doses of 3,6,9 and 12 mg at 2-minute-intervals till signs of dual AV-nodal pathway physiology or high-grade AV-block were observed by a 2-lead ECG and intra-. cardiac electrograms and were considered the end-points of infusion. St and ard electrophysiological study and induction of tachycardia were done through three femoral vein quadripolar catheters and a subclavian vein decapolar catheter. Patients were classified into hree groups according to EPS: group I included 11 [55%] patients with slow fast atrioventricular nodal reentrant tachvcardia [AVNRT]. group II included eight patients [40%] with orthodromic atrioventricular reentrant tachycardia [AVRT]. and group III included one patient [5%] with both types of tachycardias [slow/fast AVNRT and orthodromic AVRT]. Adenosine test. The mean adenosine dose used was 9 +/- 2.2mg [range 3 to 12]. Where as the mean dose that selectively blocked the antegrade fast pathway was 7.9 +/- 2 mg. Nine. six and two patients of group I, developed signs of dual AV-nodal pathways, a significant PQ-jump > 50 msec. and echo beats, respectively. Adenosine could not induce AVNRT in patients of group II. The single patient of group III had signs of dual AV-nodal pathways. None of patients in group II and III had PQ-jump or echo beats. AVNRT was induced only in two patients of group 1 and the patient of group III. Comparing both EPS and adenosine test, the latter was 83% sensitive and 88% specific for the diagnosis of dual AV-nodal physiology in patients with SVTs. Adenosine bedside test can be considered a valuable method in diagnosis and selection of patients with AVNRT from patients with narrow-complex SVT