Accuracy of exercise tolerance test in the diagnosis of coronary artery disease in patients with left dominant coronary circulation.

BACKGROUND: Exercise is a physiologic stress that helps the physicians to clarify the presence or absence of cardiovascular disease which may be obscure at rest. Although it is sensitive, its specificity is affected by several parameters, such as some metabolic conditions, some structural heart diseases, and some baseline electrocardiogram abnormalities. Currently, the relationship between coronary dominance and accuracy of EET is not examined. Therefore, this study was conducted to determine the potential impact of coronary dominance on the accuracy of EET. METHODS: In this retrospective study, data were gathered from 720 patients from four medical centers. The pattern of dominancy was determined, and the coronary dominance pattern of the patients who had normal angiograms despite abnormal EETs was compared to that from all the patients. RESULTS: Among the patients who had a normal angiogram despite an abnormal EET, 27% were left dominant while the frequency of left dominancy in the whole population of the study was only 10.9% (P=0.013). There were no significant differences in baseline characteristics, such as age and sex, between the two studied groups. CONCLUSION: The results indicated that the presence of left dominance in patients who had normal angiograms despite an abnormal EET was significantly higher than general population. Therefore, left dominance may be considered a confounding factor for EET, producing false positive results.

Comparison of Tpe Changing on ECG, in Pre and Post Dialysis and Post Transplantation.

BACKGROUND: High incidence of premature ventricular contractions (PVCS) and arrhythmia during and soon after dialysis have been demonstrated by Holter monitoring. OBJECTIVES: In this study, the effects of dialysis and renal transplantation on Tpe, Tpec (corrected Tpe), QTc (corrected QT), QTd (QT dispersion), and Tpe/QT parameters as known factors in arrhythmogenicity, and also the correlation between electrolyte and arterial blood gas changing within these parameters will be assessed. PATIENTS AND METHODS: In a retrospective study, 42 renal transplant recipients were selected. Under the supervision of an electrophysiologist, information related to Tpe, Tpec, Tpe/QT, QTd, and QTc parameters before dialysis (pre-HD), after dialysis (post-HD), and two weeks after transplantation (RTX) were analyzed. Electrolyte and arterial blood gas information were also recorded. Bonferroni adjustment, repeated measures ANOVA, generalized linear models, and generalized estimating equations were used for analysis. RESULTS: Two weeks after transplantation, the mean Tpe decreased to 0.052 ± 0.002, which was significant compared to pre-HD (P < 0.001) and Post-HD (P = 0.019). The mean Tpec was 0.059 ± 0.002, which, just in comparison to pre-HD, was significant (P = 0.005). In addition, the mean Tpe/QT decreased to 0.143 ± 0.005, which was significant compared to pre-HD (P = 0.018). The mean QTd was 0.066 ± 0.004, which wasn't significant compared to before or after dialysis. The mean QTc decreased to 0.386 ± 0.004, which was significant compared to post-HD (P = 0.0003). CONCLUSIONS: Taking the role of Tpe and Tpe/QT in arrhythmia into account and amending it by a successful transplantation can be considered as a factor that decreases arrhythmia after renal transplantation compared to ESRD patients.

Significance of a fragmented QRS complex in patients with chronic total occlusion of coronary artery without prior myocardial infarction.

OBJECTIVE: Fragmented QRS (fQRS) complexes that have numerous RSR´ patterns represent alteration of ventricular depolarization. We evaluated the relationship between fQRS and poor coronary collateral circulation and the diagnostic ability of fQRS for myocardial scar detection in patients with chronic total occlusion (CTO) without a history of myocardial infarction. METHODS: The study population consisted of patients undergoing coronary angiography with a suspicion of CAD. Seventy-nine patients with one totally occluded major coronary artery were enrolled. Exclusion criteria were history of MI; recent acute coronary syndrome; pathologic Q wave on 12-lead ECG; cardiomyopathy or severe valvular disease; coronary artery bypass surgery or percutaneous coronary angioplasty. Collateral circulation was scored on the basis of Rentrop's classification. All patients were assessed by myocardial perfusion SPECT. Fragmented QRS was characterized as existence of an R´ or R wave or S wave notch in two adjacent leads related to the location of a major coronary artery region. Single and multiple logistic regression analyses were completed in the forward method. RESULTS: Forty-nine patients had poor and 30 had well-developed collateral circulation. Fragmented QRS complexes were significantly higher in the poor collateral group (81% vs. 20%, p<0.001). Sensitivity, specificity, and the positive and negative predictive values of fQRS for myocardial scar identification were 89.4%, 87.5%, and 91.3% and 84.8%, respectively. The summed stress score and the summed rest score on SPECT were significantly higher in the poor collateral group than in the well-developed group (p<0.001) as well as in the fQRS group than the non-fQRS group (p<0.001). Logistic regression analysis revealed that the presence of fQRS was significantly and independently associated with poor collateral circulation and myocardial scar in patients with CTO. CONCLUSION: Fragmented QRS is independently related to poor coronary collateral circulation in patients with CTO without prior myocardial infarction. Notably, it can be a good predictor of myocardial scar rather than merely ischemia, with high diagnostic accuracy.

Predicting the outcome in patients with unexplained syncope and suspected cardiac cause: role of electrophysiologic studies.

OBJECTIVE: Unexplained syncope is a challenge facing electrophysiologists. The prognosis varies widely depending on underlying causes, specially, cardiac ones. We sought to determine the abnormal electrophysiolgic (EP) study results as predictors of prognosis in syncope patients with suspected cardiac cause and risk factors associated with mortality. METHODS: A total of 227 consecutive patients with unexplained syncope were prospectively enrolled in this study. EP study was performed in 177 patients in base of inclusion criteria. These patients, in whom a cardiac cause of syncope was suspected, underwent EP study and if negative, head-up tilts test (HUTT). Complete follow-up was obtained for 132 patients for 20.0±10.8 months. RESULTS: A cardiac cause of syncope was established in 35%, a neurally mediated syncope in 35.6%, and in the rest 29.4% the cause of syncope remained unexplained despite a throughout neurologic and cardiologic evaluation. Logistic analysis revealed that the significant predictors of a cardiac cause of syncope were the absence of prodromal symptoms, left bundle branch block (LBBB), sever left ventricle (LV) dysfunction and male gender. At logistic analysis, the presence of LBBB (OR=6.63; 95% CI: 1.09-40) was significantly associated with outcome of death. CONCLUSION: The present study provides evidence that presence of LBBB, abnormal EP study result and structural heart disease (SHD) have prognostic value in patients with suspected cardiac cause of syncope. The patients with SHD and unexplained syncope who had a negative EP study have a good long-term prognosis even in the presence of LV dysfunction.

The role of the fragmented QRS complexes on a routine 12-lead ECG in predicting non-responsiveness to cardiac resynchronization therapy.

OBJECTIVE: Cardiac resynchronization therapy (CRT) is introduced as a promising therapeutic option in heart failure (HF) patients with ventricular dyssynchrony.The challenge, however, is identifying the patients who are suitable candidates for this procedure. Fragmented QRS (fQRS) is associated with subendocardial fibrosis and myocardial scars. In this study, we aimed to evaluate the role of fragmented QRS complex on a routine 12-lead ECG as a predictor of response to CRT. METHODS: Sixty-five consecutive patients with HF who underwent CRT, were studied. Patients' resting 12-lead ECGs were analyzed to find presence of fQRS by a cardiologist. Echocardiographic response to CRT was defined as ≥15% decrease in left ventricular end-systolic volume (LVESV) after CRT implantation. Response to CRT was compared between patients with and without fQRS. RESULTS: The study group included 27 women (41.5%) and 38 men (58.5%) with a mean (±SD) age of 62±12 years. 27 patients (41.5%) had fQRS in their basal ECGs. Totally 46 patients (70.8%) responded to CRT in a way that the mean left ventricular ejection fraction (%) significantly increased, and left ventricular end diastolic volume (LVEDV) significantly decreased after CRT (p<0.001 and p=0.001 respectively). In multivariate logistic analysis, lack of fQRS was found to be a predictor of response to CRT (OR: 4.553, 95% CI: 1.345-15.418, p=0.015). CONCLUSION: We showed that the fQRS complex, as a sign of myocardial scar, predicts non-responsiveness to CRT. Therefore, fQRS may help selecting of CRT candidates.

Cardiomyopathy due to nonsustained ventricular tachycardia originating from the aortic sinus cusp.

We report a case of idiopathic nonsustained ventricular tachycardia (VT) originating from the aortic sinus cusp referred for presyncope and LV dysfunction and frequent premature ventricular complex with no response to 3 months anti-arrhythmic medication for heart failure and arrhythmia. She was then referred to us for frequent PVC's and runs of nonsustained VT. ECG recorded during the nonsustained VT showed a left bundle branch block pattern in the precordial leads and an inferior axis and early transition in precordial leads in V3-V4. QS morphology in lead V1 was noticed with notching on the downward deflection. Electrophysiologic study was conducted to map ventricular outflow tract as a classic method, although pace map failed to find any matched QRS with the spontaneous PVCs. The mapping of aortic cusps was also performed. The best potential was recorded in a region located at the commissure of left-right aortic cusps. A single radiofrequency energy was delivered which resulted in immediate elimination of PVCs. The patient was discharged the day after ablation without any PVC recorded on monitor. Left ventricular ejection fraction(LVEF) improved to normal level two months later. There was no PVC detected at serial holter monitoring. It seems logical not to overlook even an isolated or nonsustained ventricular arrhythmia considering the available and effective treatments such as ablation rather than congestive heart failure(CHF) therapy especially in a young patient.

Hyperglycemia-Induced T-Wave Oversensing as a Cause of Cardiac Resynchronization Therapy (CRT) Failure.

T-wave oversensing occurs when the counter starts giving dual beeps for every cardiac cycle instead of one. This usually happens when the monitoring lead displays a tall T wave, which is also sharp. R wave sensing algorithms of the devices do not sense T wave because the slow rate of the T wave is much less than that of the R wave. But the slow rate of T waves may change with time and also because of parameters like potassium levels and hyperglycemia. We present a 67-year-old female who underwent the implantation of cardiac resynchronization therapy (cardiac resynchronization and implantable cardioverter defibrilator [CRT-D]) because of severe left ventricular systolic dysfunction and ventricular dyssynchrony experienced recurrent inappropriate implantable cardioverter-defibrillator (ICD) shocks and CRT failure. Device analysis showed that the CRT failure was in consequence of T-wave oversensing due to hyperglycemia. Elimination of the T-wave oversensing after hyperglycemia control conferred good biventricular pacing and good response to CRT during a 6-month follow-up period.

Evaluation of the patients with syncope during the first month after coronary artery bypass graft.

BACKGROUND: Syncope is a well-known risk factor for adverse cardiovascular event in patients with coronary artery disease, especially those with previous myocardial infarction (MI) or left ventricular dysfunction. The aim of this study was to assess electrophysiologic findings and results of head-up tilt test (HUTT) in patients with syncope and without orthostatic changes in blood pressure during the first month after coronary artery bypass graft (CABG). MATERIALS AND METHODS: A total of 20 patients with syncope during the first month after CABG were prospectively enrolled in this study from June 2002 to April 2006. Electrophysiologic study (EPS) was performed in all of them. HUTT was performed in all of the patients regardless of the result of EPS. RESULTS: The mean age of patients was 60.3±11 years. Twelve patients were males. EPS was negative in 18 patients. HUTT was positive in 10 patients. Six patients had old MI. Ischemic insult occurred in one patient after CABG. Left bundle branch was present in two patients. There was a significant relationship between the duration of bed rest after CABG and positive HUTT (P value = 0.021). All of the patients except one did not experience syncope during the follow-up period. CONCLUSION: In patients with syncope during the first month post CABG, in whom an arrhythmic cause is suspected, the other cause of syncope like orthostatic intolerance should be considered. Being bedridden for an extended period of time post CABG can be a predisposing factor.