Study on Thermal Cycling Reliability of Epoxy-Enhanced SAC305 Solder Joint.

In this work, epoxy was added into commercial Sn-3.0Ag-0.5Cu (SAC305) solder paste to enhance the thermal cycling reliability of the joint. The microstructure and fracture surface were observed using a scanning electron microscope/energy dispersive spectrometer (SEM/EDS), and a shear test was performed on the thermally cycled joint samples. The results indicated that during the thermal cycling test, the epoxy protective layer on the surface of the epoxy-enhanced SAC305 solder joint could significantly alleviate the thermal stress caused by coefficients of thermal expansion (CTE) mismatch, resulting in fewer structural defects. The interfacial compound of the original SAC305 solder joints gradually coarsened due to the accelerated atomic diffusion, but epoxy-enhanced SAC305 solder joints demonstrated a thinner interfacial layer and a smaller IMC grain size. Due to the reduced stress concentration and the additional mechanical support provided by the cured epoxy layer, epoxy-enhanced SAC305 solder joints displayed superior shear performance compared to the original joint during the thermal cycling test. After 1000 thermal cycles, Cu-Sn IMC regions were observed on the fracture surfaces of the original SAC305 solder joint, exhibiting brittle fracture characteristics. However, the fracture of the SAC305 solder joint with 8 wt.% epoxy remained within the solder bulk and exhibited a ductile fracture mode. This work indicates that epoxy-enhanced SAC305 solder pastes display high thermal cycling reliability and could meet the design needs of advanced packaging technology for high-performance electronic packaging materials.

Impact of crystalline orientation on Cu-Cu solid-state bonding behavior by molecular dynamics simulations.

High-density electronics are hindered by the constraints of Sn-based solder joints, necessitating the exploration of Cu-Cu solid-state bonding. However, current bonding methods are expensive and time-consuming; therefore, understanding the Cu-Cu bonding mechanism is crucial for optimization. This study utilizes molecular dynamics (MD) simulation to elucidate the Cu-Cu solid-state bonding behavior, focusing on interfacial densification and diffusion phenomena. Furthermore, it highlights the influence of crystal orientation on the interfacial bonding behavior. To analyze the impact of crystal orientation, monocrystalline Cu slabs with a simplified periodic surface structure were employed to replicate surface roughness and subsequently bonded at a specific temperature. The results indicate the critical influence of crystalline orientations on the bonding process: identical orientations result in slower densification at the interface, whereas misoriented orientations significantly accelerate it. This effect, attributed to the grain boundary (GB) structures formed owing to misorientation, suggests a central role for GB diffusion in bonding progression. Diffusion coefficients calculated using the mean square displacement (MSD) confirmed these findings and exhibited significantly larger values for misoriented joints. Additionally, the simulations reveal an activation energy for GB diffusion that is lower than conventional values, highlighting the impact of the crystallographic orientation and voids at the bonding interface. Our research elucidates the role of crystalline orientation in diffusion phenomena at bonding interfaces, offering valuable implications for optimizing bonding-based manufacturing processes.

Thermomechanical Properties of Zeta (Ag3In) Phase.

The thermomechanical properties of materials within die-attach joints play an essential role in assessing the reliability of high-power modules. Ag-In transient liquid phase (TLP) bonding serves as an alternative method for die attachment. However, relevant material data for the ζ (Ag3In) phase, one of the Ag-In intermetallic compound (IMC) products of TLP bonding, are limited. This paper proposes an approach to fabricate a densified and pure bulk sample of the ζ (Ag3In) phase. The thermomechanical properties of the ζ (Ag3In) phase were subsequently investigated at elevated temperatures and compared to those of other IMCs frequently observed in die-attach joints. As the temperature increased from 30 °C to 200 °C, the hardness of the ζ (Ag3In) phase decreased linearly from 1.78 GPa to 1.46 GPa. Similarly, the Young's modulus also decreased linearly from 82.3 GPa to 66.5 GPa. These properties rank among the lowest levels compared to those of other IMCs. The average coefficient of thermal expansion within the temperature range of 70 °C to 250 °C was approximately 18.63 ± 0.61 µm/m/°C, placing the ζ (Ag3In) phase at a moderate level. When considering its potential for mitigating thermal stress, these combined properties render the ζ (Ag3In) phase an appropriate material choice for die-attach joints compared to other IMCs.

Influence of Isothermal Aging on Microstructure and Shear Property of Novel Epoxy Composite SAC305 Solder Joints.

With the rapid iteration of microsystem integrated technology, the miniaturization of electronic devices requires packaging materials with higher reliability. In this work, the microstructure evolution and mechanical properties of novel epoxy composite SAC305 solder joints were studied after isothermal aging to evaluate the enhanced effect of epoxy addition. The thickness variation and morphological evolution of the interfacial layer were analyzed. The results showed that, as the aging time was prolonged, the Cu6Sn5 interfacial layer remarkably coarsened and Cu3Sn compounds formed between the Cu6Sn5 layer and Cu pad due to the continuous atomic diffusion. Compared with the monolithic joint, the epoxy composite SAC305 joints had a lower overall IMC growth rate during aging, closely related to the initial morphologies of the interfacial layers. The shear test results showed an apparent decrease in the shear forces of all the solder joints as the aging time increased. Nevertheless, because of the extra mechanical support provided by the epoxy layer, the epoxy composite joints demonstrated notably enhanced mechanical properties. After 1000 h aging treatment, the shear force of SAC305 joints containing 8 wt.% epoxy was 26.28 N, showing a 24.08% increase over the monolithic joint. Cu-Sn IMCs were detected on the shear fracture of the monolithic joint after 1000 h aging, indicating the fracture occurred near the interface and displayed a ductile/brittle mixed fracture. Concerning the epoxy composite joints, cracks were still initiated and extended within the solder bulk, demonstrating a noticeable enhancement in ductility due to the addition of epoxy.

Solid-state bonding behavior between surface-nanostructured Cu and Au: a molecular dynamics simulation.

In recent years, solid-state bonding has attracted attention for various electronic packaging applications as an alternative to conventional solders. Surface-nanostructured materials enable solid-state bonding without complex surface modifications and operate at a low bonding temperature and pressure. Therefore, in this study, molecular dynamics simulations were conducted to investigate the solid-state bonding behavior between surface-nanostructured Cu and Au, with a focus on diffusion phenomena. A periodic ligament-cavity nanostructured Cu (NS-Cu) model was prepared at the bonding interface between Cu and Au slabs. The simulation results indicated that the larger the specific surface area of NS-Cu, the faster the densification at the bonding interface. Atomic displacement analysis showed that rapid densification occurred via the displacement of Cu and Au atoms in the vicinity of NS-Cu. The preferential diffusion of atoms along NS-Cu cavities contributed to this phenomenon. At this stage of densification, the diffusion coefficients were higher than the surface diffusion coefficients estimated based on literature, which indicates that this behavior is specific to surface-nanostructured materials. The highly disordered atomic arrangement at the bonding interface enabled significant atomic diffusion. Therefore, this study confirmed that the use of surface-nanostructured materials would contribute to a promising bonding technology for application in electronics.

Successful catheter ablation improves exercise tolerance in persistent atrial fibrillation patients, especially those with reduced ventricular contraction, preserved atrial function, or a high CHADS2 score.

BACKGROUND: It has been reported that rhythm control for persistent atrial fibrillation (per-AF) patients by catheter ablation improves their exercise tolerance, subjective symptoms, and quality of life (QoL). However, clinical factors that can predict future improvement of exercise capacity after successful catheter ablation in per-AF patients are unclear. METHODS: This study consisted of 62 patients (mean age 65.6 ±â€¯8.7 years, 77% males) with per-AF who underwent catheter ablation from June 2017 to May 2018. All patients were subjected to extended pulmonary vein isolation. Exercise tolerance was evaluated using a symptom-limited cardiopulmonary exercise test before and 3 months after catheter ablation. Primary endpoints were QoL measurements using an original questionnaire and functional assessments performed at 3 months. RESULTS: The questionnaire revealed significant improvement in QoL after catheter ablation (minimal metabolic equivalents occurring symptoms: from 5.48 ±â€¯1.14 to 5.64 ±â€¯1.06; p = 0.01). Endurance exercise characteristics improved significantly after catheter ablation, demonstrated by a shift in anaerobic threshold (from 13.3 ±â€¯3.0 to 15.2 ±â€¯3.3 ml/kg/min; p < 0.001), peak oxygen uptake (from 19.1 ±â€¯4.6 to 22.5 ±â€¯5.0 ml/kg/min; p < 0.001), and minute ventilation vs carbon dioxide production slope (from 28.3 ±â€¯6.1 to 25.7 ±â€¯3.8; p < 0.001). Multivariate Cox regression analysis revealed that a decreased left ventricular ejection fraction, high left atrial appendage velocity, and high CHADS2 score were identified as independent predictors of anaerobic threshold and a peak value of oxygen uptake with more than 20% improvement. CONCLUSIONS: Catheter ablation for per-AF patients improves QoL and exercise tolerance. The effect was especially remarkable in patients with reduced ventricular function, those who had a preserved atrial function, or those at high risk of thromboembolism.

Prognostic value of high-sensitive troponin T for predicting cardiovascular events after atrial fibrillation ablation.

BACKGROUND AND OBJECTIVES: This study aimed to evaluate the utility of high-sensitive troponin T (hs-TnT) for predicting AF recurrence and major adverse cardiovascular events (MACE) after AF ablation. METHODS AND RESULTS: A total of 227 consecutive patients with AF (mean age, 66 ± 10 years; persistent AF, n = 98) who underwent an initial ablation were enrolled. We measured hs-TnT before AF ablation and divided the patients into three groups according to the hs-TnT level: low, lesser than or equal to 0.005 µg/L (n = 54); medium, 0.006-0.013 µg/L (n = 127); and high, greater than or equal to0.014 µg/L (n = 46). We evaluated the composite endpoint of AF recurrence or MACE (including death, stroke, acute coronary syndrome, and heart failure hospitalization) after the ablation. The median hs-TnT level was 0.008 µg/L. The values of chronic kidney disease prevalence, CHA2 DS2 -VASc score, B-type natriuretic peptide level, and left atrial diameter were the highest in the high hs-TnT group among the three groups. During a mean follow-up of 15 ± 8 months, AF recurrence and MACE occurred in 56 (25%) and 9 (4%) patients, respectively. The high hs-TnT group had the highest incidence of AF recurrence and MACE among the three groups (high: 39% and 15%, medium: 22% and 2%, and low: 19% and 0%, respectively; log-rank P < .05). In multivariate analysis, hs-TnT greater than or equal to 0.014 µg/L and persistent AF were independent predictors of the composite endpoint. CONCLUSION: Hs-TnT may be a useful marker for predicting AF recurrence or MACE after AF ablation.

Multiple coronary artery spasms triggering life-threatening ventricular arrhythmia associated with the radiofrequency ablation of ganglionated plexuses of the left atrium.

We report a case of multiple coronary spasms leading to life-threatening ventricular arrhythmia, during left atrium (LA) ablation. Coronary artery spasm is a rare complication during radiofrequency catheter ablation of atrial fibrillation (AF). Previous reports mention that autonomic imbalance leads to coronary artery spasm and ST-segment elevation in the inferior leads, during trans-septal LA catheterization and AF ablation procedures. However, there are few reports detailing the association between ablation sites and changes in the electrocardiogram. We encountered transient ST-segment elevation and refractory ventricular arrhythmia, associated with coronary artery spasm, during radiofrequency ablation of ganglionated plexuses (superior surface of left and right atrium). .

Diagnostic value of electrocardiographic P-wave characteristics in atrial fibrillation recurrence and tachycardia-induced cardiomyopathy after catheter ablation.

Abnormal P-wave characteristics were reportedly associated with left ventricular interstitial fibrosis as defined by cardiac magnetic resonance images. The objective of this study is to investigate the utility of P-wave characteristics to predict atrial fibrillation (AF) recurrence and the recovery of left ventricular systolic dysfunction (LVSD) after catheter ablation (CA) for AF. Two hundred and five AF patients (109 paroxysmal and 96 persistent) who underwent CA were enrolled. We measured maximum P-wave duration (max PWD) and P-wave terminal force in lead V1 (PTFV1) calculated as a product of P-wave terminal amplitude (PTaV1) and duration (PTdV1) in lead V1 during sinus rhythm. AF recurrence was noted in 50 patients at 12 months after CA. Patients with AF recurrence had a higher prevalence of persistent AF, a larger left atrial volume, and a longer max PWD than those without. We divided the patients into 2 groups: 156 patients with left ventricular ejection fraction (LVEF) > 45% and 49 patients with LVEF ≤ 45% (Low-EF group). In Low-EF group, tachycardia-induced cardiomyopathy (TIC) was defined as improvement in LVEF ≥ 15% or LVEF ≥ 50% at 5 months after CA. TIC and non-TIC groups consisted of 37 and 12 patients, respectively. Max PWD, PTFV1, PTdV1, and PTaV1 were significantly greater in non-TIC-group than in TIC-group. PTFV1 had the highest diagnostic accuracy to discriminate between TIC and no-TIC-groups; cut-off value for PTFV1 was determined as 56.7 mV ms (area under the ROC curve = 0.80; 75% sensitivity; and 76% specificity). Max PWD was a useful predictor of AF recurrence and the complete recovery of LVSD after CA. PTFV1 had the highest diagnostic accuracy to discriminate between TIC and no-TIC-groups.

Impact of simple electrocardiographic markers as predictors for deterioration of left ventricular function in patients with frequent right ventricular apical pacing.

Several trials demonstrated that frequent right ventricular apical pacing (RVAP) was associated with cardiac dysfunction and an increased rate of heart failure hospitalization. However, there are few reports about the 12-lead electrocardiogram (12-ECG) parameters at the time of device implantation to predict deterioration of LVEF in patients with frequent RVAP. We retrospectively studied 115 consecutive patients undergoing pacemaker or implantable cardioverter-defibrillator implantation with RVAP, with rate of ventricular pacing ≥ 40% and LVEF ≥ 50% at the time of implantation. We compared the 12-ECG characteristics at the time of device implantation between patients with deterioration of LVEF (≥ 10% reduction) and those without. Twenty-nine patients (25%) had deteriorated LVEF with a decrease in mean LVEF from 59 to 40% during a median follow-up period of 8.9 [4.6-13.7] years. Multivariate logistic regression analysis showed that cumulative % of ventricular pacing [odds ratio (OR) 1.04 per 1% increase, 95% confidence interval (CI) 1.01-1.09, p = 0.04], notching of baseline paced QRS in limb leads (OR 5.04, 95% CI 1.59-19.6, p = 0.005) and the QS pattern in all precordial leads (OR 3.56, 95% CI 1.21-10.8, p = 0.02) were independently associated with deterioration of LVEF. The QS pattern of baseline paced QRS in all precordial leads had 58% sensitivity, 93% specificity for the RV lead position at the tip of RV apex. In conclusion, considering OR by multivariate analysis, notching of baseline paced QRS in limb leads and the QS pattern in all precordial leads at device implantation may be simple and useful predictors to identify patients who are at risk for deterioration of cardiac function during long-term RVAP. 12-ECG monitoring at device implantation and avoidance of the RVAP site showing a QS pattern may be important to prevent deterioration of cardiac function in patients with frequent RVAP.

Incidence and predictors of silent cerebral thromboembolic lesions after catheter ablation for atrial fibrillation in patients treated with direct oral anticoagulants.

There are few reports about the incidence and predictors of silent cerebral thromboembolic lesions (SCLs) after atrial fibrillation (AF) ablation in patients treated with direct oral anticoagulants (DOACs). The purpose of this study is to evaluate the incidence and predictors of SCLs after AF ablation with cerebral magnetic resonance imaging (C-MRI) in patients treated with DOACs. We enrolled 117 consecutive patients who underwent first AF ablation and received DOACs, including apixaban, dabigatran, edoxaban, and rivaroxaban. DOACs were discontinued after administration 24 h before the procedure, and restarted 6 h after the procedure. During the procedure, activated clotting time (ACT) was measured every 15 min, and intravenous heparin infusion was performed to maintain ACT at 300-350 s. All patients underwent C-MRI the day after the procedure. SCLs were detected in 28 patients (24%) after AF ablation. Age, female sex, the presence of persistent AF, left atrial volume, procedure time, radiofrequency energy, electrical cardioversion, and mean ACT showed no correlations with the incidence of SCLs. Multivariate analysis revealed independent predictors of SCLs were CHA2DS2VASc scores ≥3, left atrial appendage (LAA) emptying velocity ≤39 cm/s, and minimum ACT ≤260 s. Patients with both CHA2DS2VASc scores ≥3 and LAA flow velocity ≤39 cm/s had the highest incidence of SCLs 15 of 26 patients (58%). In patients treated with DOACs, CHA2DS2VASc score ≥3, minimum ACT ≤260 s, and LAA emptying velocity ≤39 cm/s were independent risk factors for the SCLs after AF ablation.

Utility of 12-lead and signal-averaged Holter electrocardiograms after pilsicainide provocation for risk stratification in Brugada syndrome.

Non-invasive risk stratification for ventricular fibrillation (VF) in Brugada syndrome (BrS) has not been fully evaluated. The aim of this study was to assess the utility of signal-averaged Holter electrocardiogram (Holter SAECG) and 12-lead Holter electrocardiogram (Holter ECG) after a pilsicainide provocation test for non-invasive risk stratification in BrS. We enrolled 30 consecutive patients with BrS [divided into 2 groups: the VF group, those with a previous history of VF (n = 10); and the non-VF group, those without a history of VF (n = 20)] and 10 control subjects without type 1 ECG. We evaluated late potentials [LP: filtered QRS (f-QRS), RMS40, and LAS40] on the Holter SAECG for 4 h after the pilsicainide provocation and in the same patients on another day without performing the pilsicainide provocation. Furthermore, we measured QRS duration and QTc interval in leads V2 and V5, and J amplitude in lead V2 on the Holter ECG after the pilsicainide provocation. On the Holter SAECG, the f-QRS at 1 h and LAS40 at 3 h after the pilsicainide provocation were significantly larger in the VF group than in the non-VF group (f-QRS at 1 h: 113.9 ± 8.9 vs. 104.9 ± 8 ms; p = 0.01, LAS40 at 3 h: 45.4 ± 5.9 vs. 35.5 ± 7.4 ms; p < 0.001). The receiver-operating characteristic curve analysis for a single parameter of VF occurrence was determined [f-QRS at 1 h: area under the curve (AUC) 0.8, with sensitivity 80% and specificity 80%; and LAS40 at 3 h: AUC 0.87, with sensitivity 90% and specificity 75%]. On the Holter ECG, there were no significant differences in these parameters between the VF and non-VF groups. In conclusion, the LP after the pilsicainide provocation using Holter SAECG may be useful for risk stratification of VF episodes in patients with BrS.

The Use of Electronic Medical Record Data to Analyze the Association Between Atrial Fibrillation and Birth Month.

OBJECTIVES: Cardiovascular disease is a condition of enormous public health concern. Recently, a population study newly revealed associations between cardiovascular diseases and birth month. Here, we investigated the association between atrial fibrillation in cardiovascular disease and birth month. METHODS: We retrospectively extracted birth date data from 6,016 patients with atrial fibrillation (3,876 males; 2,140 females) from our electronic medical records. The number of live births in Japan fluctuates seasonally. Therefore, we corrected the number of patients for each birth month based on a Japanese population survey report. Then, a test of the significance of the association between atrial fibrillation and birth month was performed using a chi-square test. In addition, we compared the results of an analysis of patient data with that of simulated data that showed no association with birth month. RESULTS: The deviations of birth month were not significant (overall: p = 0.631, males: p = 0.842, females: p = 0.333). The number of female patients born in the first quarter of the year was slightly higher than those born in the other quarters of the year (p = 0.030). However, by comparing the magnitudes of dispersion in the simulated data, it seems that this finding was mere coincidence. CONCLUSION: An association between atrial fibrillation and birth month could not be confirmed in our Japanese study. However, this might be due to differences in ethnicity. Further epidemiologic studies on this topic may result in reduction of disease risk in the general population and contribute to public health.

A case of unexpected early battery depletion caused by lithium cluster formation in implantable cardioverter-defibrillator.

Device failure from unexpected battery depletion is uncommon but can be life-threatening. Lithium cluster formation at the cathode is a novel mechanism of sudden implantable cardioverter-defibrillator (ICD) battery depletion that was first reported in 2014. We report a rare case of a 78-year-old woman with an ICD battery failure due to lithium cluster formation. Although she had never received ICD therapy, the battery voltage had dropped from 2.9 V to 2.54 V (end of life) unexpectedly for only 2 days. The prevalence of this rare phenomenon was reported to be 0.004% in 2014. However, it had gone up to 0.21% in October 2016. Both device manufacturers and clinicians should be aware of this phenomenon, and remote monitoring systems and vibratory patient notifier alerts should be considered for early detection and early treatment. .

Utility of T-wave alternans during night time as a predictor for ventricular fibrillation in patients with Brugada syndrome.

The prognostic value of T-wave alternans (TWA) during the night time in patients with Brugada syndrome (Br-S) remains unknown. We assessed TWA for risk stratification using 24-h multichannel Holter electrocardiogram (24-M-ECG) in Br-S. We enrolled 129 patients with Br-S [grouped according to histories of ventricular fibrillation (VF), n = 16; syncope, n = 10; or no symptoms (asymptomatic), n = 103] and 11 controls. Precordial electrodes were attached to the third (3L-V1, 3L-V2) and fourth (4L-V1, 4L-V2 and 4L-V5) intercostal spaces. We measured the values of maximum TWA (max-TWA) during the night time (12 a.m.-6 a.m.) and the day time (12 p.m.-6 p.m.) and calculated parameters of heart rate variability. Compared to the asymptomatic and control groups, the VF and syncope groups showed significantly greater 3L-V2 max-TWA during the night time. The cutoff value for the 3L-V2 max-TWA during the night time was determined as 20 µV (sensitivity 94 % and specificity 48 %; p = 0.01). Multivariate analysis revealed that 3L-V2 max-TWA during the night time ≥20 µV and previous VF episodes were independent predictors of future VF episodes. During a mean follow-up period of 68 ± 37 months, 16 patients experienced VF episodes. The incidence of VF episodes was the highest during the night time (p < 0.001). The 3L-V2 max-TWA during the night time may be a useful predictor for VF episodes in patients with Br-S.

Platypnea-orthodeoxia diagnosed by sitting transesophageal echocardiography.

Platypnea-orthodeoxia is a rare syndrome presenting with dyspnea and cyanosis induced by an upright position and relieved by recumbency. We report a patient with an excessively enlarged aortic root who had critical hypoxia due to a paradoxical shunt through the patent foramen ovale only when seated. The postural changes of the shunt, caused by changes in posture, were dynamically detected by transesophageal Doppler echocardiography. We believe that this syndrome should be considered when patients with aortic root dilatation present with inexplicable hypoxia, and that transesophageal Doppler echocardiography in the sitting position can be useful for detecting platypnea-orthodeoxia syndrome.

Conduction delay in right ventricle as a marker for identifying high-risk patients with Brugada syndrome.

OBJECTIVES: To evaluate the significance of conduction delay (CD) in the right ventricle (RV) in Brugada syndrome (BS) as a marker for risk stratification of sudden death. METHODS: Twenty-five patients with BS (7 with documented ventricular fibrillation (VF), 8 with syncope, and 10 without symptoms) and 10 control subjects were paced from the RV apex using 8 beats of drive pacing and a single extra-stimulus. CDs in the right ventricular outflow tract (RVOT) (CD-RV) and in the lateral left ventricle (L-LV) (CD-LV), and the local electrogram durations at a single extra-stimulus in RVOT (D-RV) and L-LV (D-LV) were calculated. We also evaluated changes in 12-lead ECG parameters in 16 patients with BS after pilsicainide challenge test (Pilsicainide-test). RESULTS: Maximal CD-RV and maximal D-RV were significantly larger than maximal CD-LV and maximal D-LV in BS (26 +/- 10 and 105 +/- 15 vs 20 +/- 6 and 92 +/- 15 ms, P < 0.05, respectively). Maximal CD-RV and maximal D-RV in patients with documented VF were the largest among the 3 groups. There was a significant positive correlation between maximal CD-RV or maximal D-RV and changes in QRS duration in leads V2 and V5 and in S wave duration in lead II and V5 after Pilsicainide-test (CD-RV; r = 0.54, 0.51, 0.56, and 0.53: D-RV; r = 0.55, 0.5, 0.57, and 0.53, P < 0.05, respectively). In control subjects, there were no significant differences. CONCLUSIONS: CD in RV was a useful marker for identifying high-risk patients with BS. CD in the RV, especially in the RVOT epicardium, may be related to arrhythmias in BS.

A predictor of positive drug provocation testing in individuals with saddle-back type ST-segment elevation.

BACKGROUND: A drug provocation test is performed to unmask a type 1 electrocardiogram (ECG) in individuals with saddle-back type ST-segment elevation in the right precordial leads (SB-ECG). The study investigated predictors of positive responders (PR) by drug testing. METHODS AND RESULTS: A total of 58 consecutive individuals with SB-ECG in lead V2 were enrolled and drug testing was performed. In leads V2 at standard and the third intercostal space (V2(IC3)), the QRS duration was measured, the amplitudes of r' wave (r'), ST-segment 20 and 40 ms after the r' wave (r'20 and r'40, respectively), the bottom of the ST-segment (ST(b)), the differences between r' and r'20 (r'-r'20), r' and r'40 (r'-r'40), r' and ST(b) (r'-ST(b)), and the descending rate of the ST-segment [(r'-r'20)/r'; DR20, (r'-r'20)/(r'-ST(b)); DR20-ST(b)] were also measured. Thirty-five PR had significantly longer QRS duration, larger r'20 and r'40, and smaller r'-r'20, DR20, and DR20-ST(b) than negative responders. DR20 and DR20-ST(b) in leads V2 and V2(IC3) were most significantly different between 2 groups. The positive and negative predictive values of ;DR20-ST(b) in lead V2(IC3) <0.62' for prediction of positive tests were 92.3% and 81.8%, respectively. CONCLUSIONS: In individuals with SB-ECG, DR20 and DR20-ST(b) in leads V2 and V2(IC3) might be useful predictors of positive testing.