Relation of ventricular repolarization to cardiac cycle length in normal subjects, hypertrophic cardiomyopathy, and patients with myocardial infarction

Ventricular Repolarization Dispersion is a Potential Risk for the Development of Life-Threatening Arrhythmia in Children with Hypertrophic Cardiomyopathy

The risk stratification and early interventions are necessary in patients with hypertrophic cardiomyopathy (HCM), as life-threatening arrhythmia (LTA) is a leading cause of death. This study aimed to explore whether an interval between the peak of the T wave to the end terminal of the T wave (Tp-e), which represents ventricular repolarization dispersion, could predict the risk for LTA in children with HCM. We analyzed electrocardiography at the first and last visits in children (aged < 15 years) with HCM, and compared Tp-e interval and the ratio of Tp-e interval to QT interval (Tp-e/QT) between children with and without LTA. We studied 25 children with HCM. During the follow-up of 85 (38-146) months, there were 7 children with LTA. The 5-year sudden cardiac death (SCD) risk was 1.4 (1.1-2.5) %, which suggested that our cohort consisted of patients at a lower risk for SCD. Age was significantly older in children with LTA compared to those without it (12.5 vs.1.0 years, P = 0.037), although sex, the presence of family history and symptoms at diagnosis, the maximum left ventricular wall thickness Z-score did not differ between the groups. At the last electrocardiography before LTA, corrected Tp-e interval and Tp-e/QT ratio were significantly greater in patients with LTA compared to those in patients without LTA (corrected Tp-e: 103 vs. 78 ms, P = 0.020; Tp-e/QT: 0.28 vs. 0.22, P = 0.046). Corrected Tp-e and Tp-e/QT ratio cutoff values of 91 ms and 0.28 yielded as the predictors for LTA with sensitivity of 85% and 72%, specificity of 71% and 89%, respectively. Prolonged absolute and corrected Tp-e intervals and an increase in the Tp-e/QT ratio can be useful predictors for LTA in children with HCM. We offer temporal assessments of ventricular repolarization dispersion to stratify the risk for the development of LTA/SCD among children with HCM.

Information Flow Between Heart Rhythm, Repolarization, and the Diastolic Interval Series for Healthy Individuals and LQTS1 Patients

Using information theoretic measures, relations between heart rhythm, repolarization in the tissue of the heart, and the diastolic interval time series are analyzed. These processes are a fragment of the cardiovascular physiological network. A comparison is made between the results for 84 (42 women) healthy individuals and 65 (45 women) long QT syndrome type 1 (LQTS1) patients. Self-entropy, transfer entropy, and joint transfer entropy are calculated for the three time series and their combinations. The results for self-entropy indicate the well-known result that regularity of heart rhythm for healthy individuals is larger than that of QT interval series. The flow of information depends on the direction with the flow from the heart rhythm to QT dominating. In LQTS1 patients, however, our results indicate that information flow in the opposite direction may occur—a new result. The information flow from the heart rhythm to QT dominates, which verifies the asymmetry seen by Porta et al. in the variable tilt angle experiment. The amount of new information and self-entropy for LQTS1 patients is smaller than that for healthy individuals. However, information transfers from RR to QT and from DI to QT are larger in the case of LQTS1 patients.

The impact of fever on myocardial repolarization parameters

BACKGROUND

It has been reported in the literature that the increase in body temperature shortens QT interval on electrocardiogram through heart rate modulation. However, the effects of fever on ventricular repolarization are not clearly known. This study elaborates on QT interval of isolated fever, corrected QT (cQT), Tp-e interval, the ratio of corrected Tp-e (cTp-e) and Tp-e/QT, and their impacts on arrhythmia potential.

METHODS

This prospective study was performed on 74 patients without any active and chronic diseases other than fever and upper respiratory tract infection. The study included patients at the age of 18-50 years suffering from fever above 38.2 °C. QT and Tp-e intervals of the patients were measured from their ECGs taken in febrile and afebrile periods. cQT and cTp-e values were calculated according to Bazett, Fridericia, and Framingham formulations.

RESULTS

QT and Tp-e intervals were observed to be shorter in the febrile period (p < 0.001 and p = 0.006 respectively). cTp-e was found to be longer in the febrile period according to Bazett, Fridericia, and Framingham formulations (p < 0.001, p = 0.002, p < 0.001, respectively). Tp-e/QT ratio was found to be higher in the febrile period than in the afebrile period (p < 0.001).

CONCLUSION

Although QT, cQT, and Tpe intervals were shorter, cTpe interval and Tpe/QT ratio were longer and higher in the febrile period, respectively. These findings may indicate that fever may create a proarrhythmic effect by causing variability in the transmural distribution of myocardial repolarization.

Prognostic value of electrocardiographic time intervals and QT rate dependence in hypertrophic cardiomyopathy

INTRODUCTION

Preventing sudden cardiac death (SCD) is one of the main goals in hypertrophic cardiomyopathy (HCM). Many variables have been proposed, however the European and American guidelines do not incorporate any ECG or Holter monitoring derived variables other than the presence of ventricular arrhythmia in their risk stratification models. In the present study we evaluated electrocardiographic parameters in risk stratification of HCM.

METHODS AND RESULTS

Novel electrocardiographic parameters including the index of cardio-electrophysiological balance (iCEB), individualized QT correction (QTi) and QT rate dependence were evaluated along with established risk factors. A composite endpoint of SCD was defined as out of hospital cardiac arrest, appropriate ICD shock and sustained ventricular tachycardia. Cox regression analysis was used to evaluate predictors of SCD. Out of the 466 HCM patients, 31 reached the composite endpoint during a follow up of 75 ± 86 months. In a multivariate model, nor iCEB, QTi or QT rate dependence were predictors of SCD. Only male gender (p < 0.01; OR 13.1; CI 1.74-98.83), negative T waves in the inferior leads (p = 0.04; OR 2.51; CI 1.03-6.13) and familial sudden death (p < 0.01; OR 3.03; CI 1.39-6.59) were significant predictors. On top of either the ESC risk score or the 3 traditional 'American risk factors', only male gender was a significant predictor of SCD.

CONCLUSION

No ECG or Holter monitoring parameters added in risk stratification for SCD in HCM. However, male gender and negative T waves in the inferior leads are promising novel markers to evaluate in larger cohorts.

Can QT/RR relationship differentiate between low- and high-risk patients with hypertrophic cardiomyopathy?

BACKGROUND

Abnormal dynamicity of repolarization is considered to be a marker of myocardial vulnerability contributing to increased risk of arrhythmic events and sudden death. However, little is known about QT dynamics in hypertrophic cardiomyopathy (HCM). In this study, we aimed to evaluate ventricular repolarization by QT dynamicity in patients with HCM, focusing on its value to define if it is able to differentiate among low- and high-risk HCM patients.

METHODS

The linear regression slopes of the QT interval, measured to the apex and to the end of the T wave plotted against RR intervals (QTapex/RR and QTend/RR slopes, respectively) were calculated from 24-hour Holter recordings using a standard algorithm in 36 HCM patients and 64 control subjects.

RESULTS

QTapex/RR and QTend/RR slopes were significantly steeper in the HCM patients in contrary to healthy control subjects (QTapex/RR = 0.22 + 0.08 vs 0.20 + 0.05, P = 0.0367; QTend/RR = 0.25 + 0.10 vs 0.20 + 0.06, P = 0.023). Moreover, the slopes of QTend/RR and QTapex/RR of high-risk patients were significantly steeper than those of control subjects while no significant differences were found among low-risk HCM patients and control subjects and only QTe/RR of high-risk patients was significantly different between low- and high-risk HCM patients.

CONCLUSIONS

Our study results suggest that QT dynamicity is impaired in patients with HCM and may help to differentiate among low- and high-risk patients. Further studies are needed to elucidate the prognostic significance and clinical implications of impaired ventricular repolarization in patients with HCM.

Pressure overload. Heart Fail Clin. 2012;8:21-32. [PMID: 22108724 DOI: 10.1016/j.hfc.2011.08.005]

This review discusses cardiac consequences of pressure overload. In response to elevated pressure, the ventricular hypertrophy compensates for the increased wall stress. However, the ventricular hypertrophy involves numerous structural adaptations that may lead to ventricular dysfunction and, eventually, heart failure. Particular emphasis is placed on molecular mechanisms that govern the development of hypertrophy and that may lead to maladaptive structural changes resulting in adverse cardiac events.

Ventricular repolarization dynamicity and arrhythmic disturbances after beating-heart and arrested-heart revascularization

BACKGROUND

Arrhythmias attributable to altered autonomic modulation of the heart, with elevated sympathetic and depressed vagal modulation, occur to a similar extent after surgery performed on beating or arrested hearts. Coronary artery bypass grafting (CABG) with cardiopulmonary bypass has been associated with more frequent occurrence of arrhythmic events than surgery performed without CABG, even with comparable levels of postoperative cardiac autonomic (dis) regulation after arrested- and beating-heart revascularization. We explored the effects of arrested- and beating-heart revascularization procedures on the dynamics of ventricular repolarization and on increased postoperative arrhythmic events.

METHODS

Study participants included 57 CABG patients; 28 underwent on-pump and 29 underwent off-pump procedures. The 2 groups were comparable regarding clinical and postoperative characteristics. With high-quality 15-minute digital electrocardiograms, we assessed ventricular repolarization dynamics using RR and QT intervals and analyzed QT variability (QTV) and QT-RR interdependence. RR and QT intervals were determined from stationary 5-minute segments. QT-interval variability was determined by a T-wave template-matching algorithm. We used linear regression to compute the slope/correlation of the QT/RR interval. The Fisher exact test, nonpaired t-test, and ANOVA were applied to test the results; P <.05 was considered significant.

RESULTS

Postoperative arrhythmic events were significantly more frequent in both groups. One week postoperatively these events were significantly more frequent in the on-pump group. In both groups, the RR interval was shorter after CABG (P <.001). The QT variability index increased from -1.2 + or - 0.6 to -0.8 + or - 0.4 after off-pump CABG and from -1.3 + or - 0.5 to -0.5 + or - 0.6 on day 4 after surgery (P <.05), further deteriorating to -0.2 + or - 0.6 one week after CABG in the on-pump group only (P <.05). QT-RR correlations decreased from 0.39 to 0.24 in the off-pump vs 0.34 to 0.17 in the on-pump group (P <.05), and in both groups they remained significantly reduced for as long as 4 weeks after CABG.

CONCLUSIONS

For both on- and off-pump CABG, beat-to-beat heart-rate changes and rate-dependent ventricular repolarization adaptation showed disparities that worsened after surgery. The observed repolarization lability after CABG procedures seems to be transient but more pronounced after on-pump CABG. The association of arrhythmic events with ventricular repolarization lability changes in the setting of faster heart rates offers novel insights into the mechanisms of perioperative proarrhythmia after beating- and arrested-heart revascularization.

Dynamic QT/RR relationship of cardiac conduction in premature infants treated with low-dose doxapram hydrochloride

Doxapram hydrochloride, a respiratory stimulant, has several undesirable side effects during high-dose administration, including second-degree atrioventricular (AV) block and QT prolongation. In Japan, this drug is contraindicated for newborn infants. Recent studies, however, have demonstrated the efficacy and safety of doxapram therapy for apnea of prematurity (AOP) using lower doses than those previously tested. As a result, approximately 60% of Japanese neonatologists continue to use this drug. This study used surface ECG recordings to assess the cardiac safety of low-dose doxapram hydrochloride (0.2 mg/kg/h) in fifteen premature very-low-birth-weight infants with idiopathic AOP. Cardiac intervals and number of apnea episodes were compared before and after drug administration. Low-dose doxapram hydrochloride resulted in approximately 90% reduction in the frequency of apnea without side effects. None of the infants developed QT or PR prolongation, arrhythmia, or other conduction disorders. In addition, there was no change in the slope of QT/RR before versus after administration of doxapram hydrochloride. We conclude that low-dose administration of doxapram hydrochloride did not have any undesirable effects on myocardial depolarization and repolarization.

Cardiac repolarization and its relation to ventricular geometry and rate in reverse remodelling during antihypertensive therapy with irbesartan or atenolol: results from the SILVHIA study

Hypertensive left ventricular (LV) hypertrophy is associated with a substantial risk for malignant arrhythmias and sudden death. According to recent results, antihypertensive therapy with the angiotensin II type 1 receptor blocker irbesartan reverses both structural and electrical remodelling. However, the relation between the LV geometric pattern (concentric vs eccentric) and electrical reverse remodelling has not been characterized, neither has the relation between repolarization and rate (QT/RR and JT/RR relation), which presumably reflects the propensity for bradycardia-dependent ventricular arrhythmia. In this study, repeat echocardiographic and electrocardiographic measurements were performed in hypertensive patients with LV hypertrophy, randomized to double-blind therapy with irbesartan (n = 44) or the beta(1)-adrenoceptor blocker atenolol (n = 48) for 48 weeks; 53 patients had concentric and 39 eccentric LV hypertrophy. In addition, 37 matched hypertensive subjects without LV hypertrophy and no current therapy served as controls. Irbesartan induced structural and electrophysiological reverse remodelling, independent of LV geometry. In contrast, atenolol had similar beneficial effect only in patients with concentric LV hypertrophy, while the response in those with eccentric hypertrophy was unfavourable with both prolonged repolarization time and an increased QT/RR slope (suggesting reverse-use dependence). In conclusion, there is a significant geometry-related difference in the reverse remodelling processes induced by irbesartan and atenolol. Echocardiographic characterization of the geometry in hypertension-induced LV hypertrophy might become an important step in the selection of optimal antihypertensive therapy.

Electrocardiographic abnormalities in methamphetamine abusers

AIMS

Although many adverse cardiovascular outcomes are mentioned in conjunction with methamphetamine use, a causal relationship between methamphetamine use and arrhythmia or cardiomyopathy has not been demonstrated in man. Clinical experience with methamphetamine users suggested a higher incidence of electrocardiographic abnormalities. This study seeks to quantify that incidence, among subjects enrolled in a study of adults with methamphetamine dependence.

METHODS

Electrocardiograms obtained during screening in a previous clinical trial were examined. The study population (n = 158) of adults with methamphetamine dependence [Diagnostic and Statistical Manual version IV (DSM IV-TR)] was drawn from five sites across the United States, recruited in the interval 2002-03.

RESULTS

A significant variance from the normal population was noted in the electrocardiograms of the study cohort. Among the abnormalities was a prolongation of the QTc beyond 440 ms in 27.2% of the group. QTc prolongation to this extent poses a particular risk for ventricular arrhythmias, most notably torsades de pointes.

CONCLUSIONS

We believe that this is the first demonstration of clinically significant QTc prolongation in a methamphetamine-using population, and that this has implications for the types of arrhythmias for which this population is at risk. It may further provide a marker for risk of cardiomyopathy. The fact of electrocardiographic changes with potential cardiac risks may be useful in a motivational interviewing approach, in challenging the methamphetamine user's basis for continuing use.

Impact of Diabetes on QT Dynamicity in Patients With and Without Myocardial Infarction: The KORA Family Heart Study

INTRODUCTION

Patients with diabetes mellitus (DM) have an unfavorable prognosis after myocardial infarction (MI), partially due to a higher risk of sudden cardiac death (SCD). QT dynamicity is an independent predictor of SCD in post-MI patients. However, the effects of diabetes on QT dynamicity in patients with MI have not been described.

METHODS

We studied 468 survivors of MI (67 with DM) from the population-based MONICA registry (KORA Family Heart Study), Augsburg, Germany, by standardized questionnaire, anthropometry, electrocardiogram (ECG), 30-minute-Holter-ECG-recordings and echocardiography. In addition, 422 siblings without prior MI (22 with DM) were studied by the same protocol.

RESULTS

Among post-MI patients, the QT/RR slope was significantly steeper in diabetics than in nondiabetics (0.096 +/- 0.057 vs 0.077 +/- 0.045; P = 0.002). Likewise, among siblings without MI, the QT/RR slope was steeper in diabetics than in nondiabetics (0.104 +/- 0.053 vs 0.080 +/- 0.042; P = 0.008). The association of DM with steeper QT/RR slope remained significant in multivariate models in post-MI patients (beta: -0.14; P = 0.004) as well as in individuals without MI (beta: -0.10; P = 0.047).

CONCLUSIONS

In a large population of survivors of MI and unaffected siblings, patients and siblings presenting with DM exhibited an abnormal QT rate-dependence, compared with individuals without DM in both groups. Thus, diabetes itself may be a major determinant of ventricular arrhythmias, independently of a previous MI. These observations might in part explain the higher incidence of sudden cardiac death and ventricular arrhythmias in patients with DM.

Novel indices of ventricular repolarization to screen post myocardial infarction patients

We propose novel indices of ventricular repolarization intervals, the JTp/JT, Tpe/JTp and Tpe/JT ratios. These indices have been compared with the duration of the ventricular repolarization intervals and other ratios in 17 normal subjects and 17 patients with old myocardial infarction. In the intervals and other ratios, the best separation between groups is obtained with the Tpe/QTp and Tpe/QT ratios with 94% sensitivity and 82% specificity, the proposed ratios increased sensitivity to 100% and specificity to 94%. These indices should be further tested to determine their usefulness in discriminating between OMI patients with and without susceptibility to ventricular arrhythmias.

Importance of hepatitis C coinfection in the development of QT prolongation in HIV-infected patients

BACKGROUND

Case reports and unblinded studies suggest that human immunodeficiency virus (HIV) disease is associated with QT prolongation and torsade de pointes ventricular tachycardia. Hepatitis C coinfection is common in patients with HIV disease, and cirrhosis is also associated with QT prolongation. We therefore undertook a systematic analysis of the role of liver injury, nutritional state, and coinfection with hepatitis C in the etiology of QT prolongation in HIV disease.

METHODS

We performed a blinded, controlled retrospective cohort study of 1648 patients over a 3-year period at a university-affiliated municipal hospital. All electrocardiograms were included if patients with HIV disease had measurements of CD4 count and viral load within 3 months and serum electrolytes within 30 days (n = 816). Control subjects were chosen randomly from the general medicine service (n = 832). QT interval was measured in lead II and corrected for heart rate by Bazett's formula (QTc).

RESULTS

QTc was slightly but significantly longer in patients with HIV disease than in controls (443 +/- 37 vs 436 +/- 36 milliseconds, P < .001). Patients with hepatitis C had more pronounced QTc prolongation (452 +/- 41 vs 437 +/- 35 milliseconds, P < .001). CD4 count, HIV viral load, and HIV medications had no effect on QTc. When patients with hepatitis C were excluded from the analysis, there was no statistical difference between patients with HIV disease and controls (438 +/- 34 vs 436 +/- 36 milliseconds, P = .336). Multiple linear regression revealed that both HIV and hepatitis C infection predicted QTc prolongation, as did age, female sex, history of hypertension, use of opiates, low serum K+ and albumin, and high AST. Hepatitis C coinfection nearly doubled the risk of QTc of 470 milliseconds or greater in patients with HIV disease (29.6% vs 15.8%, P < .001).

CONCLUSIONS

Human immunodeficiency virus and hepatitis C infections both independently prolong QTc. Coinfection with hepatitis C greatly increases the likelihood of clinically significant QTc prolongation in patients with HIV disease.

Gender Differences in the Dynamics of Terminal T Wave Intervals

This study was designed to investigate gender differences in the dynamic changes of the terminal T wave (Ta-e interval) of healthy subjects. Holter ECGs were recorded in 24 healthy volunteers (12 men aged 23 +/- 2 years). The intervals from QRS onset to the apex (QaT) and to the end of the T wave (QeT), and the interval between the apex and the end of the T wave (Ta-e) were measured. Then, the QeT/RR, QaT/RR, and Ta-e/RR relationship was evaluated by linear regression analysis in each subject. The QeT and QaT intervals were significantly longer in women than men and the slope of the QeT/RR and QaT/RR relationship was steeper in women than men. The Ta-e intervals showed a significant but weaker positive correlation with the preceding RR intervals in 7 (58.3%) men and 9 (75.0%) women. The average values of the slope and the correlation coefficient of the Ta-e/RR relationship were significantly smaller compared to those of QeT and QaT in both men and women (P < 0.0001). The slope of the Ta-e/RR relationship was significantly greater in women than men (0.025 +/- 0.009 vs 0.011 +/- 0.012, P < 0.005). However, the Ta-e intervals were significantly longer over the entire range of RR intervals in men than women (P < 0.0001). The rate-correcting formulas of Bazett and Framingham overcorrected the Ta-e intervals. The observed gender difference in the measurement and dynamics of the Ta-e interval may help to understand the mechanisms underlying the gender difference in the incidence of ventricular arrhythmias.

Impact of Infarct-Related Artery Flow on QT Dynamicity in Patients Undergoing Direct Percutaneous Coronary Intervention for Acute Myocardial Infarction

Background— Complete coronary artery reperfusion in acute myocardial infarction (AMI) has been shown to significantly improve survival. Electrical stability may be the decisive mechanism for this beneficial effect. Because electrical stability is largely dependent on ventricular repolarization, we sought to determine the impact of a modern reperfusion strategy (ie, direct percutaneous coronary intervention [PCI]) on QT dynamicity in AMI and examined its association with infarct-related artery flow.

Methods and Results— We prospectively investigated QT dynamicity in 128 patients undergoing direct PCI for a first AMI. Slopes and correlation coefficients of the linear QT/RR regression were determined in the time interval before reperfusion, within the initial hour after reperfusion, and within the remaining recording period from Holter ECG recordings, which were initiated on admission. Subgroup analysis based on TIMI 3 (n=100) and TIMI 2 (n=28) flow after PCI revealed no significant differences in QT/RR slope before PCI (0.145±0.12 versus 0.160±0.19, P =NS). After PCI, QT/RR slopes increased only in the TIMI 2 subgroup ( P <0.05). In TIMI 2 patients, QT/RR slopes were significantly steeper in the hour after PCI and in the remaining recording period, respectively (0.155±0.12 versus 0.192±0.15, P <0.05, and 0.159±0.10 versus 0.210±0.17, P <0.01).

Conclusions— Alterations of QT dynamicity in patients with incomplete reperfusion may suggest an altered electrical restitution, potentially providing a substrate for serious ventricular arrhythmias. Thus, our findings offer new insights into mechanisms by which complete reperfusion may affect electrical stability.

Gender differences in ventricular repolarization: terminal T wave interval was shorter in women than in men

The incidence of sudden death is lower in women than in men, although women have a longer QT interval and are more prone to develop torsades de points than men. It has been recently proposed that the time interval between the apex and end of the T wave (Ta-e) represents the transmural dispersion of ventricular repolarization. Gender and age differences in Ta-e interval have not been fully assessed previously. Standard surface 12-lead ECGs recorded in 760 healthy subjects (382 women, 0-88 years of age) were studied. The intervals from j-point to the apex of the T wave (JaT) and to the end of the T wave (JeT) were measured in lead V5 in each ECG and corrected by preceding RR intervals using the formula of Bazett (JaTc and JeTc). The Ta-e and Ta-e/JeT ratio were also evaluated. Both JaTc and JeTc intervals were significantly longer in women aged > 20 years than in men of the same age (P < 0.0001). The difference was due to shortening of these intervals after puberty in men. However, the Ta-e interval was significantly shorter in women than in men (P < 0.05) and subsequently the Ta-e/JeT ratio was significantly smaller in women than in men (P < 0.0001). The results showed gender differences in the Ta-e interval and JaTc and JeTc intervals in healthy adults, and suggest that the small transmural dispersion of repolarization in women, in spite of the long JaTc and JeTc intervals, might be a beneficial antiarrhythmic property.

Relationship between the QT indices and the microvolt-level T wave alternans in cardiomyopathy

The relationship between the QT indices and microvolt-level T wave alternans (TWA) is unknown in cardiomyopathy, so the present study examined 86 patients with cardiomyopathy who experienced TWA during exercise testing (EXT). The QT interval (QT), duration from the Q wave to the peak of the T wave (QTp), duration from the peak to the end of the T wave and the dispersion of these parameters were measured by 12-lead electrocardiogram at rest and during EXT. In dilated cardiomyopathy (DCM), TWA was positive (TWA+) in 19 patients and negative (TWA-) in 17. No significant difference was observed between the TWA+ and TWA- groups in any parameter. In hypertrophic cardiomyopathy (HCM), TWA was positive in 24 patients and negative in 12. Max QTc, max QTpc and mean QTpc during EXT in the TWA+ group were significantly longer than those in the TWA- group. The sensitivity of TWA for ventricular tachycardia (VT) was high in DCM and HCM, and that of max QTc >500 ms during EXT for VT was high in HCM (93%). TWA is a useful predictor for VT in DCM and HCM, and prolonged max QTc during exercise has a prognostic value in HCM. Repolarization abnormality during exercise plays an important role in the genesis of VT in cardiomyopathy.

Prolongation of QT interval and ventricular septal hypertrophy

Long QT syndrome (LQTS) is a prime example of interplay between molecular biology, cellular physiology, and organ physiology. Both the congenital and acquired forms of LQTS are due to intrinsic and/or acquired abnormalities of the ionic currents responsible for cardiac repolarization. We analyzed the QTc interval, QRS axes and interventricular septal thickness (IVST) in 41 patients who had a prolonged QT interval on routine electrocardiography (ECG) (5 females and 36 males, mean age 65+/-13 years). The QRS axis of patients in the LQTS group (27+/-49 degrees) was significantly lower (p < 0.05) than in the control group (46+/-26 degrees). However, the IVST in the LQTS group (10+/-2 mm) was significantly thicker than in the control group (9+/-1 mm) (p < 0.05), while the WTd was not significantly different. The QTc interval in patients with ventricular septal hypertrophy (IVST > or = 12 min, 478.8+/-7.9 msec) was significantly longer (p < 0.05) than in the normal group (IVST < 12 mm, 472.1+/-17.5 msec). In conclusion, the results of this preliminary study suggest that prolongation of the QT interval on ECG should prompt screening for electrocardiographic evidence of ventricular hypertrophy in patients with this disease.