82-rubidium positron emission tomography determined myocardial flow reserve and outcomes following cardiac revascularisation - A multicentre registry study

BACKGROUND

Finding patients with chronic coronary syndromes (CCS) whom revascularization could benefit, is complicated. Myocardial flow reserve (MFR), a measurement of myocardial perfusion, has proven prognostic value on survival and risk of major adverse cardiac events (MACE). We investigated if MFR identifies who may benefit from revascularization.

METHODS

Among 7462 patients from Danish hospitals examined with 82Rb PET between January 2018 and August 2020, patients with ≥5% reversible perfusion defects were followed for MACE and all-cause mortality. Associations between revascularisation (within 90 days) and outcomes according to MFR (< and ≥ 2) was assessed by Cox regression adjusted by inverse probability weighting for demographics, cardiovascular risk factors, comorbidities, and 82Rb PET variables.

RESULTS

Of 1806 patients with ≥5% reversible perfusion defect, 893 (49%) had MFR < 2 and 491 underwent revascularisation (36.6% in MFR < 2 versus 17.9% MFR ≥ 2, p < 0.001). During a median follow-up of 37.0 [31.0-45.8 IQR] months, 251 experienced a MACE and 173 died. Revascularisation was associated with lower adjusted risk of all-cause mortality (hazard ratio [HR], 0.51 [95% CI, 0.30-0.88], p = 0.015) and MACE (HR, 0.54 [0.33-0.87], p = 0.012) in patients with MFR < 2 but not MFR ≥ 2 for all-cause mortality (HR 1.33 [0.52-3.40], p = 0.542) and MACE (HR 1.50 [0.79-2.84], p = 0.211). MFR significantly modified the association between revascularisation and MACE, but not all-cause mortality (interaction p-value 0.021 and 0.094, respectively).

CONCLUSIONS

Revascularization was associated with improved prognosis among patients with impaired MFR. No association was seen in patients with normal MFR. In patients with regional ischemia, MFR may identify patients with a prognostic benefit from revascularization.

Diagnostic accuracy and reclassification potential of the acoustic CADScor algorithm in intermediate risk patients with suspected coronary artery disease

Background

Validation studies of the 2019 European Society of Cardiology pre-test probability model (ESC-PTP) for coronary artery disease (CAD) report that 35–40% of patients have intermediate pre-test risk (ESC-PTP 5-&lt;15%). A clear strategy for deferral or referral in this group has not been established. Stratification tools with a high negative predictive value (NPV) are especially wanted to improve pre-test risk estimates.

Acoustic detections of coronary stenosis are a new technology which could potentially be useful to supplement PTP stratification. One of the devices, the CADScor®System, has been shown to down-classify &gt;40% of patients to low risk without increasing CAD prevalence. However, the clinical utility of using the CADScor algorithm (version (V)3.1) has not be validated.

Purpose

1) To validate the diagnostic performance of the CADScor®System (V3.1), and 2) to study the reclassification potential of a clinical likelihood strategy by ESC-PTP estimation supplemented by a CAD-score.

Methods

In total, 1732 patients without known CAD but with symptoms suggestive hereof underwent coronary CTA as a first-line diagnostic test. Based on an interview prior to coronary CTA, the ESC-PTP model was applied and sound recordings were performed using the acoustic CADScor® System. Patients with a suspected &gt;50% diameter stenosis in any coronary segment at coronary CTA were referred to investigation with Invasive angiography (ICA) with measurement of Fractional flow reserve (FFR).

The ESC-PTP risk estimation was divided according to the recommended cut-offs of &lt;5%, 5-&lt;15% and &gt;15% PTP of obstructive CAD. Haemodynamically obstructive CAD was defined as: (1) FFR value &lt;0.80, (2) luminal diameter stenosis reduction &gt;90%, or (3) luminal diameter stenosis reduction ≥50% if FFR was indicated but not performed. A predefined cut-off value of 20 was used for CAD-score values to rule-out CAD.

Results

A suspected stenosis was found in 439 patients (26%) after coronary CTA. The follow up with ICA with FFR showed significant stenoses in 198 patients (12%).

In the entire cohort using the ≤20 CAD-score cutoff for CAD rule-out, sensitivity was 85.3% (95% CI 79.5–89.9%), specificity was 40.3% (95% CI 37.8–42.9%), the PPV was 5.9% (95% CI 13.8–18.3%)), and the NPV was 95.4% (95% CI 93.4–96.9%). Hence, the disease prevalence of obstructive CAD was 4.6% in the ruled-out patients.

Applying the ≤20 CAD-score cutoff for CAD rule-out in intermediate risk patients (ESC-PTP 5-&lt;15%) a total of 316 patients (48%) were down-classified to low risk with an obstructive CAD prevalence of 3.5%.

Conclusion

Having high NPV, the CADscor holds excellent rule-out power. Interestingly, the CADscor has reclassification properties in intermediate CAD risk patients where almost 50% can be deferred form further testing without increasing obstructive CAD risk. Thus, the CADscor can supplement clinical assessment to guide decisions on the need for further testing.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): The study was supported by the Health Research Fund of Central Denmark Region, Aarhus University Research foundation and by an institutional research grant from Acarix A/S, Denmark. Patient flowReclassification potential

P5630Morphometric and qualitative differences in neointimal tissue six months after implantation of bioresorbable scaffolds versus conventional everolimus eluting stents in ISAR-Absorb MI trial

Background

Bioresorbable scaffolds (BRS) are novel devices designed to overcome the long-term limitations of permanent metallic stent implantation. Optical coherence tomography (OCT) surveillance can provide important insights on the process of vessel wall healing at follow-up.

Purpose

We sought to compare OCT-assessed healing at 6 months after implantation of everolimus-eluting BRS and everolimus-eluting metallic stents (EES) in patients treated for acute myocardial infarction (AMI).

Methods

ISAR-Absorb MI is a multicentre, 2:1 randomized trial comparing outcomes of patients with AMI stented with BRS or conventional EES. Angiographic surveillance was planned for all patients at 6–8 months follow-up. Patients who had OCT surveillance at follow-up were included for the present analysis. Analysis of contiguous OCT cross-sections- 1 mm apart was performed at a centralized core laboratory. Tissue characterisation using a 256-level grey-scale signal intensity (GSI) analysis was also performed for all neointimal regions of interest (ROI) with thickness of 100 to 400 μm. ROI's were classified as mature using a standard cut-off GSI score of 109.7. Generalised linear mixed model (GLMM) was used as appropriate. Statistical analysis was performed using R software. Data is presented as numbers, percentages or median (Interquartile range, IQR).

Results

Median follow-up interval was 216 days. 70 patients in the BRS arm and 33 patients in the EES arm were available for analysis. Stented length was 19.8 mm (13.6, 24.5) and 22.3 mm (16.7, 26.4) in BRS and EES arms respectively (p=0.73). Minimum lumen area [5.13 (3.95, 6.71) vs. 4.83 (3.63, 6.92) mm2] and minimum stent area [5.78 (4.88, 7.34) vs. 6.36 (4.70, 7.45) mm2] were comparable between BRS and EES.

2,262 frames (1,529 in BRS, 733 in EES) with 20,033 struts (12,704 in BRS, 7,329 in EES) were assessed. Overall strut coverage was better with BRS compared to EES (97.5% vs. 91.1% respectively, p<0.001). Malapposed (1.1% vs. 0.5%, p=0.54) and uncovered struts (7.3% vs. 1.3%, p<0.001) were more common with EES. Neointimal coverage was comparable amongst both stent groups [85.5 (61.9, 124.1) vs. 71.5 (33.4, 133.0) μm in BRS and EES groups respectively, p=0.50].

GSI analysis in 95 cases (65 cases, 2,233 ROIs in BRS; 30 cases, 1,210 ROIs in EES) showed that immature ROIs were numerically more common in the EES group as compared to the BRS group (75.4 vs. 57.0% respectively; p=0.35).

Two-year clinical follow-up and analysis of correlation of clinical outcomes with OCT findings will also be available for presentation at ESC Congress 2019.

Conclusions

In selected patients undergoing OCT imaging at 6–8 months after implantation of BRS and conventional EES for AMI, we observed generally favourable healing characteristics with high rates of strut coverage, low rates of strut malapposition and fewer areas of immature neointimal areas with BRS in comparison to EES.

Acknowledgement/Funding

The study was predominantly funded by Deutsches Herzzentrum München and in part by a grant from Abbott Vascular

P2713A genetic risk score improves discrimination of hemodynamically obstructive coronary artery disease (CAD) beyond the CAD Consortium scores in patients at low-to-intermediate risk of CAD

Background

Genetic risk scores (GRSs), based on variants identified in genome-wide association studies (GWAS), have been shown to predict risk of coronary artery disease (CAD). However, the clinical potential remains unknown.

Purpose

To investigate whether a GRS improves discrimination of hemodynamically obstructive CAD beyond the CAD Consortium scores and coronary artery calcium score (CACS) in patients referred for coronary computed tomography angiography (CTA).

Methods

We consecutively included and genotyped 1645 patients undergoing CACS scoring and coronary CTA on a suspicion of CAD. Using LDPred, a recently validated GRS was calculated as the weighted sum of the number of CAD risk variants identified from the CARDIoGRAMplusC4D GWAS meta-analysis. Patients with a ≥50% stenosis on CTA further underwent invasive coronary angiography (ICA) with fractional flow reserve (FFR). Hemodynamically obstructive CAD was defined as a visual ICA stenosis >90%, FFR <0.80, or a quantitative coronary analysis stenosis >50% if FFR was not feasible. Discrimination was evaluated by receiver-operating characteristics.

Results

Median age was 57 (interquartile range 50–64) years and 799 (49%) were males. Hemodynamically obstructive CAD was present in 14 (4%) with a low GRS (<20th percentile), 91 (9%) with an intermediate GRS (20th–80th percentile) and 53 (16%) with a high GRS (>80th percentile) (p<0.0001). Adding the GRS improved the area under the receiver-operating curve (AUC) on top of the CAD Consortium basic score (from 0.67 to 0.72, p=0.0052), and the CAD Consortium clinical score (0.70 to 0.74, p=0.0084), but not on top of the CAD Consortium clinical score + CACS (0.85 to 0.86, p=0.30). Improvement in discrimination on top of the CAD Consortium scores was predominantly driven by females ≤57 years (CAD Consortium basic score ± GRS: 0.60 to 0.78, p=0.0004; CAD Consortium clinical score ± GRS: 0.63 to 0.78, p=0.0007). The GRS did not improve discrimination in any subgroups including CACS (CAD Consortium clinical score + CACS ± GRS: all p-values >0.05).

Conclusion

A GRS improves discrimination of hemodynamically obstructive CAD beyond CAD consortium scores, particularly in young women. However, the additive discriminative value is attenuated in models including CACS.

479Preoperative global longitudinal strain is the best predictor of mortality following transcatheter aortic valve replacement

Background

Prognosis after transcatheter aortic valve replacement (TAVR) is variable. This might depend on preoperative evaluation of myocardial performance by other measurements than ejection fraction (EF).

Purpose

The aim of this study was to investigate the predictive value of preoperative global longitudinal strain (GLS) and the guidelines specified subtypes of aortic stenosis (AS) on mortality following TAVR.

Methods

We included 511 patients with severe AS who underwent TAVR in the period July 2012–June 2017.

Patients were divided into guidelines-specified subgroups based on EF (EF: ≥50 (NEF) or <50% (LEF)), peak gradient (PG: ≥4 (HG) or <4 m/s (LG)) and flow status (stroke volume index (SVI): ≥35 (NF) or <35 ml/min/kg (LF)): (1) HG-NEF (n=228), (2) HG-LEF (n=91), (3) LG-LF-NEF (n=71) and (4) LG-LF-LEF (n=121). We also investigated the effect of replacing EF by GLS in the guideline specified subgroups (GLS ≤−14 (HGLS) and GLS >−14% (LGLS)).

Results

Mean follow up time was 1033 days. Mean age was 80.2±7.1 years. Median overall survival was 5.3±0.3 years. Comorbidity burden was higher in patients with LF – and LEF status in terms of a higher median plasma creatinine (103 [85; 135], p<0.001) and EurologII score (6.1 [3.4; 9.6], p<0.001).

LG-LF-LEF AS was associated with a significantly worse outcome compared with all other groups (p<0.005, Fig. 1A). High gradient status, irrespective of EF (p=0.88), was associated with the best prognosis with a median survival of 5.0±0.5 and 5.5±0.1 years for NEF and LEF, respectively.

Overall and in patients with HG-NEF, impaired GLS (>−14%) was associated with poor outcome (Fig. 1B–D). There was a trend towards a poorer prognosis with GLS >−14% in LG-LF-NEF AS (p=0.10).

In an univariate analysis impaired GLS >−14% (HR 2.04, p<0.005), LG-LF-LEF status (HR 1.82, p=0.001), PG <4m/s (HR 1.74, p=0.001) and tricuspid regurgitation gradient >30 mmHg (HR 1.63, p<0.001) were significant predictors of mortality in contrast to EF, SVI, age, gender and plasma creatinine.

GLS >−14% emerged as the only significant outcome predictor in a multivariate analysis (HR 1.93, p<0.05).

Figure 1

Conclusion

Impaired global longitudinal strain >−14% was the best individual echocardiographic predictor of overall survival in symptomatic severe AS and could identify a subgroup of patients with HG-NEF AS with a worse prognosis.

Influence of Cardiac CT based disease severity and clinical symptoms on the diagnostic performance of myocardial perfusion

We aimed to identify factors influencing the sensitivity of perfusion imaging after an initial positive coronary computed tomography angiography (CCTA) using invasive coronary angiography (ICA) with conditional fractional flow reserve (FFR) as reference. Secondly we aimed to identify factors associated with revascularisation and to evaluate treatment outcome after ICA. We analysed 292 consecutive patients with suspected significant coronary artery disease (CAD) at CCTA, who underwent perfusion imaging with either cardiac magnetic resonance (CMR) or myocardial perfusion scintigraphy (MPS) followed by ICA with conditional FFR. Stratified analysis and uni- and multiple logistic regression analyses were performed to identify predictors of diagnostic agreement between perfusion scans and ICA and predictors of revascularisation. Myocardial ischemia evaluated with perfusion scans was present in 65/292 (22%) while 117/292 (40%) had obstructive CAD evaluated by ICA. Revascularisation rate was 90/292 (31%). The overall sensitivity for perfusion scans was 39% (30-48), specificity 89% (83-93), PPV 69% (57-80) and NPV 68% (62-74). Stratified analysis showed higher sensitivities in patients with multi-vessel disease at CCTA 49% (37-60) and typical chest pain 50% (37-60). Predictors of revascularisation were multi-vessel disease by CCTA (OR 3.51 [1.91-6.48]) and a positive perfusion scan (OR 4.69 [2.49-8.83]). The sensitivity for perfusion scans after CCTA was highest in patients with typical angina and multiple lesions at CCTA and predicted diagnostic agreement between perfusion scans and ICA. Abnormal perfusion and multi vessel disease at CCTA predicted revascularisation.

Spontaneous coronary artery dissection: a Western Denmark Heart Registry study

BACKGROUND

Spontaneous coronary artery dissection (SCAD) is a rare cause of acute coronary syndrome (ACS) that associates with a high acute-phase mortality rate, whereas long-term outcome is less well described.

OBJECTIVE

To describe the incidence, predictors, and prognosis of SCAD.

DESIGN

Retrospective case-identification study from the Western Denmark Heart Registry and the database of the Forensic Institute at Aarhus University from 1999 through 2007.

RESULTS

SCAD was documented in 22 of 32,869 (0.7 per thousand) angiograms in the angiographic registry. The SCAD incidence among cases of ACS was 22 of 11,175 (2.0 per thousand). None was seen in the forensic database. The mean age was 48.7 +/- 8.9 years (range: 37-71 years). Females constituted 17 of 22 (77%) patients and all had undergone one or more pregnancies; two cases occurred in the postpartum period. The left descending artery (LAD) was the predominant site of entry. The age distribution, prevalence of the cardiovascular risk factors, presence of coronary atherosclerosis, and entry of the dissection were comparable among genders. Treatment was percutaneous coronary intervention in 13 of 22 (59%), coronary artery bypass operation in 2 of 22 (9%), and medical treatment in 7 of 22 (32%) patients. The mean follow-up period was 3.6 +/- 2.9 years. One patient suffered from recurrent SCAD; another patient died suddenly. The MACE- (cardiac death, nonfatal myocardial infarction, and new revascularization) free survival was 81% after 24 months.

CONCLUSION

SCAD is a rare disease that mainly affects younger women. Compared with earlier reports, the prognosis seems to be improved by early diagnosis and interventional treatment.

Reproducibility of QT parameters derived from 24-hour ambulatory ECG recordings in healthy subjects

AIM

To estimate the reproducibility of QT parameters derived from 24-hour ambulatory ECG recordings.

METHOD

Ten healthy volunteers aged 25 to 41 years participated. In two 24-hour ambulatory ECG recordings obtained 1 day apart, the QT interval was measured manually at stable heart rates in approximately 16 periods during daytime and 6 periods during nighttime. The association between the QT and RR interval was described by linear regression for day and nighttime separately and the following QT parameters were calculated: the QT interval at heart rate 60 beats/min during daytime (QT(60)day), slope(day), slope(night), and the difference in QT(60) between day and nighttime (DeltaQT(60)). The QT parameters were assessed four times for each participant to discriminate method inaccuracy from day to day variation. The reproducibility was estimated as the coefficient of repeatability, the relative error, and the ratio between within-subject variability and between-subject variability.

RESULTS

The coefficient of repeatability, the relative error and the ratio, respectively, were 19 ms, 1.8% and 0.5 for QT(60)day, 0.076, 21% and 0.68 for slope(day), 0.116, 43% and 1.37 for slope(night), and 37 ms, 325% and 1.19 for DeltaQT(60) when estimating the overall day to day reproducibility. Inaccuracy of QT measurement accounted for approximately 40% of this variation, whereas the error caused by selecting segments was small.

CONCLUSION

QT(60)day has a high reproducibility and may with advantage replace the conventional QT interval measured on a resting ECG. To assess QT dynamics, the slope of the regression line during daytime is suitable and the short term reproducibility acceptable for clinical trials. Regarding slope(night) and DeltaQT(60), the variation is high and the parameters should be used with caution.

Dose-related cardiac electrophysiological effects of intravenous magnesium. A double-blind placebo-controlled dose-response study in patients with paroxysmal supraventricular tachycardia

AIMS

The role of magnesium as an antiarrhythmic drug is yet not conclusive. Therefore, we performed a double-blind, randomized, placebo-controlled dose-response study of cardiac electrophysiological effects of intravenous magnesium.

METHODS AND RESULTS

Thirty-six patients undergoing an electrophysiological evaluation for paroxysmal supraventricular tachycardia were randomized to one of the following dosages of intravenous magnesium (0, 5, 10 or 20 mmol). Conventional electrophysiological variables for sinus node function, atrial, atrioventricular node and ventricular conduction and refractoriness were measured before and after magnesium administration. Prolongation of the atrial-His interval was found at 5 mmol of magnesium compared with placebo and no further prolongation was observed at higher doses (-3 +/- 8, 11 +/- 9, 7 +/- 15, 11 +/- 16, for the dosages of 0, 5, 10 and 20 mmol of magnesium, respectively, P < 0.05). Measures of sinus node function, intra-atrial conduction and conduction through the Purkinje system were unaffected by magnesium. Male gender was associated with prolongation in atrial effective refractory period, in contrast to shortening in females: 2 +/- 43, 35 +/- 44, 36 +/- 33, 13 +/- 12 ms for males and 3 +/- 6, -12 +/- 11, -13 +/- 12, 0 +/- 23 ms for females, respectively (P < 0.001).

CONCLUSION

Atrioventricular node conduction was prolonged by 5 mmol intravenous magnesium and no further prolongation was observed at higher dosages. At dosages of 5 and 10 mmol magnesium the atrial effective refractoriness was prolonged in males and shortened in females.

Increased QT dispersion in patients with insulin-dependent diabetes mellitus

AIM

To compare the QT dispersion in unselected patients with insulin-dependent diabetes mellitus to non-diabetic control subjects and to assess the association between the QT dispersion and cardiac autonomic neuropathy, ischaemic heart disease, blood pressure level and nephropathy.

METHODS

42 patients with insulin-dependent diabetes mellitus and 80 control subjects aged 40-57 years participated. The QT interval was measured in a resting 12-lead electrocardiogram (ECG) and the QT dispersion defined as the difference between the maximum and minimum QT interval. Bazett's formula was used to correct for heart rate (QTc). The degree of cardiac autonomic neuropathy was assessed by five function tests and ischaemic heart disease was defined by a previous myocardial infarction, ECG abnormalities or a positive exercise test.

RESULTS

Compared to control subjects, diabetic patients had a longer QTc interval (433 vs. 416 ms; P=0.002) and a higher QT dispersion (36 vs. 30 ms; P=0.02). In the diabetic group, the QTc interval was prolonged in patients with autonomic neuropathy (449 vs. 420 ms; P=0.007) and the QT dispersion was increased in patients with ischaemic heart disease (51 vs. 33 ms; P=0.004). No association was found to urinary albumin excretion rate or blood pressure.

CONCLUSION

The QT dispersion as well as the QTc interval is increased in patients with insulin-dependent diabetes mellitus. The association between QT dispersion and ischaemic heart disease indicates that abnormalities in cardiac repolarisation may be caused by complications to diabetes rather than diabetes in itself.

Efficacy and safety of intravenously administered dofetilide in acute termination of atrial fibrillation and flutter: a multicenter, randomized, double-blind, placebo-controlled trial. Danish Dofetilide in Atrial Fibrillation and Flutter Study Group

BACKGROUND

This study was designed to assess the efficacy and safety of intravenous dofetilide in acute termination of atrial fibrillation (AF) and flutter (AFL). Dofetilide, an investigational class III antiarrhythmic agent, selectively inhibits the rapid component of the delayed rectifier potassium current, thus prolonging the effective refractory period and duration of the action potential. Dofetilide can be administered intravenously and has a rapid onset of electrophysiologic action.

METHODS AND RESULTS

Ninety-six patients with AF (n = 79) or AFL (n = 17) with a median arrhythmia duration of 62 days (range 1 to 180) were randomized to placebo (n = 30) or 8 micrograms/kg IV dofetilide (n = 66) over 30 minutes. Conversion was defined as termination of the atrial arrhythmia within 3 hours from the start of infusion. The conversion rate was 30.3% after dofetilide and 3.3% after placebo (P <.006). Conversion rate was higher in AFL than in AF: 64% versus 24% (P =. 012). In nonconverters, there was no statistically significant difference between the change in heart rate among the dofetilide-treated compared with the placebo-treated patients (P =. 42). Torsade de pointes ventricular tachycardia developed in 2 patients (3%). In both patients, drug infusion was discontinued before the event because of prolongation of the QT interval.

CONCLUSIONS

Intravenous dofetilide is effective in acute termination of AF and AFL of medium duration, with a particularly high efficacy rate in AFL. A small but serious risk of proarrhythmia must be anticipated.

Population effects of the bombing of Oklahoma City

BACKGROUND AND PURPOSE

The explosion at the Murrah Federal Building in Oklahoma City on April 19, 1995, affected many members of the community as well as direct victims. Our goal was to measure the exposure and effects among the general population.

METHODS

We conducted surveys of the Oklahoma City metropolitan area and a control area to measure exposure and impact, primarily stress and psychological distress.

RESULTS

Of the adults in the Oklahoma City MSA, 61.5 percent (58.5 percent to 64.5 percent with 95 percent confidence) reported experiencing at least one direct result of the bombing. In population terms, about 433 thousand adults (between 412 thousand and 457 thousand, with 95 percent confidence) were exposed to one or more of the consequences of the bombing. Oklahomans reported higher rates (about double) of increased alcohol use, smoking more or starting smoking. They reported more stress (about double), psychological distress (about double), post-traumatic stress-disorder components, and intrusive thoughts (double) related to the bombing than in the control area. Oklahomans also reported higher rates of seeking help for their stress or taking steps to reduce stress. The differences persisted into 1996, more than a year after the bombing.

CONCLUSION

The exposure to the bombing was widespread, including more than half the adults in the metropolitan area surrounding Oklahoma City. The psychological effects were high and, while decreasing, persisted more than a year after the bombing. Primary care practitioners should screen their patients, who may normally not be considered victims, for exposure to the effects of a terrorist disaster for an extended period of time.

Predicting abuse-prone parental attitudes and discipline practices in a nationally representative sample

OBJECTIVE

According to sociological and ecological models of abuse, typically nonabusive parents could behave abusively towards their children under certain circumstances. The purpose of this study was to examine factors that place parents at risk of abusing their children by predicting parents' use of discipline practices and attitudes that may bias parents towards abusive behaviors, which we refer to as abuse-proneness.

METHOD

A telephone interview was administered by the Gallup Organization to a nationally representative sample of 1,000 parents. Using a set of theoretically relevant risk factors, multiple regression was used to predict variations in parental attitudes (i.e., attitudes towards physical discipline and attitudes that devalue children) and parental discipline practices (i.e., physical discipline, nonphysical discipline, and verbal abuse).

RESULTS

The findings confirmed the importance of examining elements of parental attitudes, history, personality characteristics, as well as religion and ideology in predicting abuse proneness. Child age also was an important predictor in all analyses except predicting parental attitudes that devalue children. The findings suggest also, however, that it may be unduly simplified to regard parents as somewhere on a continuum of nonpunitive to punitive disciplinarians. Social isolation was not a significant predictor in any of the analyses.

CONCLUSIONS

Although many important theoretical predictors of abuse proneness were confirmed, many questions arise regarding the diversity of discipline practices that parents use, and the relevance of child's age and social isolation in predicting abuse proneness. Implications for practitioners and future research are discussed.

Increased left ventricular systolic function in insulin dependent diabetic patients with normal albumin excretion

Alterations in cardiovascular function may be an aetiological factor for the development of microalbuminuria in patients with insulin-dependent diabetes mellitus. We studied cardiac function with echocardiography in relation to the degree of albuminuria in 27 insulin-dependent diabetes mellitus patients and 13 healthy subjects. Patients were grouped according to urinary albumin excretion: <20 microg x min(-1) (normoalbuminuric), and 20 to 200 microg x min(-1) (microalbuminuric). None were or had been treated with cardiovascular drugs. The normoalbuminuric patients had a higher heart rate, mean velocity of circumferential shortening, stroke velocity index (a measure of contractility), and aortic peak velocity than controls. No difference in diastolic function was present. In the microalbuminuric group, the stroke velocity index was comparable to values observed in healthy subjects. The increased systolic performance (heart rate and contractility) may contribute to the renal hyperperfusion and glomerular hyperfiltration observed in insulin-dependent diabetes mellitus patients before the development of micro- and in turn macroalbuminuria. The possible cause effect mechanisms should be further studied, as preventive medical treatment of the hypercontractile heart is possible. In conclusion, cardiac contractility is increased in insulin-dependent diabetes mellitus patients with normoalbuminuria and returns to levels observed in healthy subjects when microalbuminuria develops.

Recovery of beat-to-beat variations of QRS

There is a growing interest in the analysis of beat-to-beat variations of the morphology (BBM) of cardiac waves in electrocardiograms (ECG). Such analyses are confronted with the low BBM-to-noise ratio. An ECG clustering technique is introduced that brings the benefits of signal averaging to BBM analysis and recovers the beat-to-beat pattern of BBM. ECG clustering aligns waves and sorts them into clusters. The precision of the alignment was enhanced by sub-sample alignment. Kohonen's self-organising neural networks identified the clusters of the cardiac waves during training. The subsequent clustering of a wave results in a label for the closest cluster, a distance to the cluster and optimal alignment. Furthermore, ECG clustering avoids base-line variations and amplitude modulation sufficiently to be applied to the QRS wave in the raw ECG. The technique is demonstrated on 14 subjects with coronary heart disease and no myocardial infarction, myocardial infarction, or inducible ventricular tachycardia. ECG clustering is a general-purpose technique for beat-to-beat analysis, where the variations are cyclic as in the sinus rhythm. Results show that beat-to-beat variations in the QRS morphology are in general cyclic, with a main period of about four cardiac cycles. All calculations were performed with the Cardio software.

Effect of parasympathetic blockade on the signal-averaged electrocardiogram

Low parasympathetic activity is associated with late potentials detected at a noise level of 0.4 microV in a signal-averaged electrocardiogram (SAECG) following myocardial infarction. In contrast, at a noise level of 0.2 microV, lowering parasympathetic activity influences late potential parameters in the opposite direction in healthy subjects. The aim of this study was to estimate the relationship between parasympathetic activity and the SAECG obtained at noise levels of 0.4 and 0.2 microV in healthy subjects. Two SAECG recordings in 10 healthy subjects were obtained at noise levels of 0.2 and 0.4 microV before and after parasympathetic blockade using atropine (1 mg). Signal-averaged QRS duration (SA-QRS), late potential duration (LPD) defined as duration of terminal signals below 40 microV, and root mean square voltage of the terminal 40 ms of the averaged QRS (RMS40) were measured. At a noise level of 0.2 microV SA-QRS reduced from 124 +/- 14 to 114 +/- 17 ms (P = 0.008), LPD from 37 +/- 10 to 28 +/- 14 ms (P = 0.01), and RMS40 increased from 26 +/- 22 to 41 +/- 25 microV (P = 0.006) during parasympathetic blockade compared to baseline values. At a noise level of 0.4 microV the SA-QRS (115 +/- 15 ms) and LPD (29 +/- 11 ms) were lower and the RMS40 (37 +/- 23 microV) was higher compared to the noise level 0.2 microV, and no systematic alterations of the three variables were found during parasympathetic blockade. The parasympathetic nervous system may induce a very low-amplitude late potential in the SAECG. The data suggest that parasympathetic activity and a low noise level may lead to a false late potential-positive SAECG in low arrhythmia risk subjects. Therefore, we recommend the use of a noise level of 0.4 microV or identification of high arrhythmia risk patients by late potential and low parasympathetic activity.

[From paroxysmal to chronic atrial fibrillation]

Chronic atrial fibrillation is by definition always preceded by paroxysmal atrial fibrillation. The electropathophysiological mechanisms underlying paroxysmal atrial fibrillation are reviewed: atrial electrophysiological inhomogeneity, atrial ectopic activity, and cardiac autonomic dysfunction. Safe and effective interventions that prevent the progression from paroxysmal into chronic atrial fibrillation have not yet been developed. Such developments should be given high priority, as the consequences of chronic atrial fibrillation--stroke and heart failure--are unacceptable.

Efficacy and safety of dofetilide, a new class III antiarrhythmic agent, in acute termination of atrial fibrillation or flutter after coronary artery bypass surgery. Dofetilide Post-CABG Study Group

Ninety-eight patients, who developed atrial fibrillation/flutter after coronary artery bypass grafting within 1-6 days after surgery, were included into a double-blind, placebo-controlled, randomized trial to assess the efficacy and safety of dofetilide. Patients were randomly allocated to dofetilide 4 micrograms/kg i.v. (n = 33), dofetilide 8 micrograms/kg i.v. (n = 32) or placebo (n = 33) given intravenously over 15 min at a constant infusion rate. Responders were defined as patients who converted to sinus rhythm at any time during the initial 3 h after the start of the infusion. The conversion rates were 24% (8/33) on placebo, 36% (12/33) on dofetilide 4 micrograms/kg, and 44% (14/32) on dofetilide 8 micrograms/kg. The P-values (two-tailed) were 0.27 for dofetilide 4 micrograms/kg vs. placebo, 0.11 for dofetilide 8 micrograms/kg vs. placebo, and 0.10 for dose-response relationship. Short episodes of aberrant ventricular conduction and ventricular tachycardia were seen separately in three subjects after dofetilide 8 micrograms/kg. No episodes of torsades de pointes were noted. No negative inotropic effect was noted. In conclusion, dofetilide was well tolerated, but the effects on atrial fibrillation/flutter did not attain statistical significance, possibly due to the high placebo conversion rate.

Effect of residual noise level on reproducibility of the signal-averaged ECG

Late potentials are detected at various noise levels in clinical studies. The aim of this study was to assess the effect of residual noise level on the reproducibility of the signal-averaged electrocardiogram (ECG). Two consecutive raw 15-minute ECG from each of 188 patients with coronary artery disease were digitized and stored on optical discs. Each raw ECG was analyzed by two signal-averaging procedures to noise level 0.2 microV or 0.4 microV. Standard time-domain parameters were measured: QRS duration (SA-QRS), late potential (LP) duration, and root-mean-square voltage of the terminal 40 ms of the filtered QRS (RMS40). The SA-QRS was prolonged by 12 +/- 14 ms by the reduction in noise level from 0.4 microV to 0.2 microV, LP duration was prolonged by 10 +/- 10 ms, and RMS40 was reduced by 19 +/- 22 microV. The temporal variation of the measured SA-QRS from ECG1 to ECG2 was significantly lower at noise level 0.2 microV (9 +/- 13 ms) than at noise level 0.4 microV (13 +/- 14 ms) (P < .001). The LP duration was also more stable at noise level 0.2 microV than at noise level 0.4 microV (0.5 +/- 11 ms vs 2 +/- 13 ms, P < .05). The presence of any two of three abnormal parameters (SA-QRS > 120 ms, RMS40 < 25 microV, LP duration > 40 ms) was used as the criterion for the presence of LPs. At noise level 0.4 microV, the proportion of patients with diagnosed LPs in ECG1 was 25% and at noise level 0.2 microV it was 62%. At noise level 0.4 microV, 20% were reclassified from LP-negative in ECG1 to LP-positive in ECG2, and 7% were reclassified from LP-positive in ECG1 to LP-negative in ECG2. At noise level 0.2 microV, 20% were reclassified from LP-negative in ECG1 to LP-positive in ECG2, and 9% were reclassified from LP-positive in ECG1 to LP-negative in ECG2. It was concluded that (1) the diagnosis of LPs is significantly dependent on the extent of noise reduction by signal averaging: and (2) the numerical reproducibility of signal-averaged QRS duration and LP duration is lower at noise level 0.4 microV then at noise level 0.2 microV; and the diagnostic reproducibility of LPs is similar at both noise levels.

[Atrial fibrillation after coronary artery bypass surgery. The significance of preoperative vagus modulation and ectopic atrial activity]

To investigate the impact of pre-operative autonomic balance and atrial ectopic activity on the risk of atrial fibrillation or flutter after aorto-coronary artery bypass surgery 24-hour Holter monitoring was analyzed in 102 patients before coronary artery bypass grafting. Index for vagal tone was calculated as % successive RR-interval differences > 6%. Twenty-nine (28%) of the 102 patients developed atrial fibrillation or flutter. Independent predictors (90% confidence interval) of postoperative atrial fibrillation or flutter were identified by logistic regression analysis: the independent predictors were older age, relative risk 1.07/year (1.02-1.12), vagal index < 10%, relative risk 4.50 (1.40-14.5), > or= 10 ectopic supraventricular beats/24 hour, relative risk 3.03 (1.05-8.72), and one or more event of non-sustained supraventricular tachycardia, relative risk 3.02 (1.11-8.22). Thus, age of the patient, attenuated preoperative cardiac vagal modulation, ectopic supraventricular beats, and paroxysmal non-sustained supraventricular tachycardia are independent risk factors for the development of atrial fibrillation or flutter after coronary artery bypass surgery.

Re-evaluation of the role of P-wave duration and morphology as predictors of atrial fibrillation and flutter after coronary artery bypass surgery

To evaluate the significance of P-wave duration and morphology for the development of post-operative atrial fibrillation/flutter, we investigated 189 consecutive patients scheduled for elective coronary artery bypass surgery. The longest pre-operative total P-wave duration was measured from the standard electrocardiogram at a paper speed of 50 mm.s-1 (mean of two independent observers). By the signal averaging technique we determined the pre-operative total P-wave duration, and root-mean square voltage of the last 10, 20, and 30 ms of the filtered (40-250 Hz) P-wave from a vector composite of three orthogonal leads at noise level 0.2 microV. Forty-two (22%) of the patients developed atrial fibrillation/flutter. Older age (mean +/- SD) 62 +/- 8 vs 56 +/- 8 years (P < 0.000), increasing body weight 83 +/- 11 vs 79 +/- 12 kg (P = 0.05), treatment for hypertension 26 vs 13% (P = 0.04), and a longer P-wave duration in the standard electrocardiogram 129 +/- 12 vs 124 +/- 12 ms (P = 0.01) were associated with development of atrial fibrillation/flutter documented by a 12-lead electrocardiogram. Logistic regression analysis identified independent predictors, estimated adjusted relative risk (95% confidence interval) of atrial fibrillation/flutter: with age > 60 years, the relative risk was 4.46 (2.05-9.73), and body weight > 80 kg, the relative risk was 3.81 (1.71-8.46). Thus, P-wave duration and morphology did not provide significant information on the risk of atrial fibrillation/flutter when controlling for the effects of increasing age and body weight.

Noise in the signal-averaged electrocardiogram and accuracy for identification of patients with sustained monomorphic ventricular tachycardia after myocardial infarction

Late potentials are detected at various noise levels in clinical studies. The aim of this study was, in a case-control design, to assess the effect of residual noise level on the identification of patients with sustained monomorphic ventricular tachycardia after myocardial infarction. Electrocardiograms from 16 patients with prior myocardial infarction and documented sustained monomorphic ventricular tachycardia and 41 patients with prior myocardial infarction and without ventricular tachycardia, were analysed by two signal averaging procedures to noise level 0.2 and 0.4 muV. Standard time domain parameters were measured. Two definitions of late potential were analysed: (1) if any two of the following criteria were present (signal-averaged QRS duration > 120 ms, late potential duration > 40 ms, and root-mean-square voltage of the terminal 40 ms of the filtered QRS < 25 muV); or (2) if the signal-averaged QRS duration > or = 120 ms. Overall the signal-averaged electrocardiogram performed better at noise level 0.4 muV compared to noise level 0.2 muV with respect to identification of patients with or without ventricular tachycardia after myocardial infarction. Reducing noise level from 0.4 to 0.2 muV increased the sensitivity, but the consequence was a substantial decrease in specificity. Our data indicate that when a high sensitivity is the goal, the definition based only on signal-averaged QRS duration > or = 120 ms should be applied; sensitivity was 88% and specificity 59% at noise level 0.4 muV. If a high specificity is the goal, the definition should be based on the definition with two abnormal parameters; sensitivity was 69% and specificity 68% at noise level 0.4 muV.

[Treatment with implantable cardioverter-defibrillators. Experiences from Skejby hospital during the period 1989-1994]

The aim of the present study was to evaluate survival and therapy for ventricular tachyarrhythmia in patients treated with implantable cardioverter-defibrillator (ICD)-implantation at Skejby Hospital. Seventy-two patients, of which 54 were male, have received an ICD since 1989. Mean (range) age was 54 (16-74) years. Forty-nine (68%) had ischaemic heart disease. The patients were followed for a median (range) of 14 (1/2-50) months. Kaplan-Meyer plots are presented for total mortality, cardiac mortality, sudden cardiac mortality, appropriate therapy, and therapy for life-threatening tachyarrhythmia. After one, two and three years respectively, mortality was respectively 13, 27, and 32%, cardiac mortality was 5, 19, and 24%, sudden cardiac mortality was 3, 6, and 12%, cumulative incidence of appropriate therapy was 56, 66, and 90%, and cumulative incidence of therapy for life-threatening tachyarrhythmia was 19, 29 and 52%. It is concluded, that the majority of patients treated with an ICD developed ventricular tachyarrhythmia and had appropriate or lifesaving ICD-therapy during follow-up.

Within- and between-patient variation of the signal-averaged P wave in coronary artery disease

OBJECTIVES

To estimate interobserver, within-patient and between-patient variation of the signal-averaged P wave. To determine whether demographic, clinical, conventional ECG information, and coronary angiographic data are associated with the signal-averaged P wave duration in patients with documented coronary artery disease.

BACKGROUND

A prolonged signal-averaged P wave may indicate the presence of a substrate for atrial tachyarrhythmias and may predict subsequent development of atrial fibrillation. However, information on variation, reproducibility, and determinants of the signal-averaged P wave are sparse.

METHODS

One hundred ninety-three patients with angiographically documented coronary artery disease underwent two consecutive procedures of signal-averaging of P waves (SAECG1 and SAECG2). Interobserver, within-patient, and between-patient variation of the signal-averaged P wave was estimated (coefficient of variation: SD/mean). Multiple linear regression analysis was applied to identify parameters independently associated with signal-averaged P wave duration (SA-P). Atrial late potentials were considered if SA-P > 140 ms, and logistic regression analysis was applied to identify parameters associated with the presence of atrial late potentials.

RESULTS

The interobserver, within-patient, and between-patient coefficients of variation for the signal-averaged P wave duration were 7.5%, 6.0% and 8.4%, respectively. The signal-averaged P wave duration correlated significantly with standard ECG P wave duration and height of the patient (r = 0.59). Forty-nine percent of the patients had atrial late potentials. P wave duration in the standard ECG correctly classified 73% (140/188) of the patients with respect to atrial late potential positivity or negativity. The sensitivity was 67% and the specificity was 78%. Agreement on the presence or absence of atrial late potentials between two observers was present in 71% (136/193) of the patients, and in 78% (151/193) between SAECG1 and SAECG2.

CONCLUSIONS

The signal-averaged P wave has limited reproducibility in patients with coronary artery disease, and a normal or abnormal signal-averaged P wave can be predicted from the conventional ECG with high accuracy. It is recommended that the signal-averaged P wave be compared with the standard ECG P wave duration in follow-up studies with the aim of predicting atrial fibrillation.

The signal-averaged ECG becomes late potential-positive at low noise levels in healthy subjects

Late potentials are detected at various noise levels in clinical studies. The aim of this study was to quantify the effect of residual noise level on the signal-averaged ECG. Thirty minutes of raw ECG (lead -X, +X, -Y, +Y, -Z, and +Z) from 10 healthy volunteers were digitized and stored on optical discs. Each ECG was analysed by four signal averaging procedures to noise level 0.1, 0.2, 0.3, and 0.4 microV, respectively. At each noise level, time domain analysis of the filtered vector (40-250 Hz) included determination of the QRS duration (QRS), late potential duration (LPD, duration of terminal signals below 40 microV), and root-mean-square voltage of the terminal 40 ms of the filtered QRS (RMS40). On average, the measured signal-averaged QRS duration was prolonged by 7.0 ms (range 0.9-12.5 ms) per 0.1 microV reduction in noise level. Late potential duration increased by 5.9 ms (range 0.2-10.0 ms) per 0.1 microV reduction in noise level, and RMS40 was reduced by 9.1 microV (range 0.5-20.2 microV) per 0.1 microV reduction in noise level. At noise level 0.4 microV, 0.3 microV, 0.2 microV, and 0.1 microV the number of late potential-positive subjects were 1, 2, 4, and 6, respectively. Late potential parameters are significantly dependent on noise level after signal averaging. Using conventional criteria for late potentials, healthy subjects become false-positive at low noise levels. Establishment of standards for noise level is recommended.

Premature atrial beat eliciting atrial fibrillation after coronary artery bypass grafting

Of patients undergoing coronary artery bypass grafting 30% develop atrial fibrillation (AF) or flutter. To determine if AF is initiated from the right or left atrium, atrial electrograms were continuously recorded in patients undergoing this procedure. In addition, to study whether the prematurity index of premature atrial contractions (PACs) eliciting AF differs from PACs not provoking AF, the distribution of prematurity indices was evaluated from R-R interval analysis. The right and left atrial recording electrodes were first activated by the ectopic beat provoking AF in six and eight patients, respectively. The prematurity index of the PAC eliciting AF was located in the middle (in half of the patients) or to the left of the median distribution of prematurity indices. The variability in activation of the atrial electrodes suggests that the PAC provoking AF can have its origin in the right, the septal, or the left region of the atrium. The initiation of AF depends on the prematurity index of the PAC.

Hemodynamic predictors of atrial fibrillation or flutter after coronary artery bypass grafting

The cumulated incidence of atrial fibrillation or flutter after coronary artery bypass grafting is 30%. The causes of these arrhythmias have not yet been sufficiently identified. We therefore undertook the present study to analyze the possible association of hemodynamic function during the various phases of coronary artery bypass grafting and the later development of atrial fibrillation/flutter. Hemodynamic function was measured with a pulmonary artery catheter in 120 consecutive patients undergoing elective coronary artery bypass surgery. Thirty-five (29%) of the patients developed atrial fibrillation/flutter. Logistic regression analysis identified independent predictors of atrial fibrillation/flutter. After induction of general anesthesia, the relative risk (95% confidence interval) of older age was 1.09/year (1.03-1.16), and the reduction in relative risk by an increase in left ventricular stroke work was 0.96/gm (0.93-0.99). After weaning from the extracorporeal circulation the independent significant predictors were age, relative risk 1.07/year (1.01-1.13), and increased central venous pressure, relative risk 1.12/mm Hg (1.00-1.26). At the time of admission to the intensive care unit, the relative risk of age was 1.10/year (1.03-1.18), and the relative risk of an increased central venous pressure was 1.26/mm Hg (1.06-1.49). However, the best prediction model (prediction after induction of general anesthesia) only provided a median predicted probability of atrial fibrillation/flutter of 0.37 for the patients who had atrial fibrillation/flutter, and a median predicted probability of atrial fibrillation/flutter of 0.20 for the patients without these arrhythmias. We identified possible hemodynamic predictors of atrial fibrillation/flutter after coronary bypass surgery, but the use of a risk stratification for development of atrial fibrillation/flutter based on hemodynamic function cannot be recommended.

Atrial ectopic activity and atrial fibrillation/flutter after coronary artery bypass surgery. A case-base study controlling for confounding from age, beta-blocker treatment, and time distance from operation

To evaluate the impact of ectopic atrial activity and cardiac autonomic function for development of atrial fibrillation or flutter we studied 128 consecutive patients undergoing elective coronary artery bypass grafting. The patients were Holter monitored during a 96-h postoperative period. Autonomic balance was estimated by heart rate variability measurement. Thirty-eight (30%) patients developed sustained atrial fibrillation or flutter. Holter recordings were analyzed in a case-base design matching for age, beta-blocker treatment, and time elapsed after the operation. The number of supraventricular ectopic beats/h was increased (P < 0.01) in the case group during each of the last 7 h before onset of atrial fibrillation or flutter. Episodes of supraventricular tachycardia 62% vs. 26%; cases vs. controls (P = 0.007), episodes of non-sustained atrial fibrillation 29% vs. 0% (P = 0.0009), and episodes of non-sustained atrial flutter 15% vs. 0% (P = 0.05) were significant predictors of atrial fibrillation or flutter. Mean heart rate/h was increased in each of the 24 h preceding the arrhythmia. However, indexes of autonomic heart function did not differ significantly between groups. Patients developing atrial fibrillation or flutter after coronary artery bypass surgery present 'warning' atrial arrhythmias: numerous supraventricular ectopic beats, paroxysmal supraventricular tachycardia, and episodes of nonsustained atrial fibrillation and flutter.

Low vagal tone and supraventricular ectopic activity predict atrial fibrillation and flutter after coronary artery bypass grafting

To investigate the impact of pre-operative autonomic balance and atrial ectopic activity on the risk of atrial fibrillation or flutter after aorto-coronary artery bypass surgery 24-h Holter monitoring was analysed in 102 patients before coronary artery bypass grafting. Index for vagal tone was calculated as % successive RR interval differences > 6%. Twenty-nine (28%) of the 102 patients developed atrial fibrillation or flutter. Independent predictors (90% confidence interval) of postoperative atrial fibrillation or flutter were identified by logistic regression analysis: the independent predictors were older age, relative risk 1.07.year-1 (1.02-1.12), vagal index < 10%, relative risk 4.50 (1.40-14.5), > or = 10 ectopic supraventricular beats . 24 h-1, relative risk 3.03 (1.05-8.72), and one or more events of non-sustained supraventricular tachycardia, relative risk 3.02 (1.11-8.22). Thus, age of the patient, attenuated pre-operative cardiac vagal modulation, ectopic supraventricular beats, and paroxysmal non-sustained supraventricular tachycardia are independent risk factors for the development of atrial fibrillation or flutter after coronary artery bypass surgery.

[Late ventricular potentials after myocardial infarction]

Late potentials in the QRS complex can be detected with signal-averaged electrocardiography and are associated with delayed and disorganized ventricular activation. This article reviews the technique, describes the pathophysiological basis of late potentials, and assesses the prognostic value of late potentials for subsequent development of ventricular tachyarrhythmias and sudden cardiac death in postmyocardial infarction patients.

Contractile function of right ventricular papillary muscle after left ventricular infarction in rats: effects of early and late inhibition of angiotensin converting enzyme

Alterations in the right ventricular function may or may not contribute to progressive cardiac dysfunction after left ventricular infarction. Ligation of the left coronary artery (LCAL) was lethal within 24 h for 25% of 100 rats, whereas none of 21 sham-operated rats died. No rats died during the following 4 weeks, after which the ischaemic area of the left ventricular wall appeared fibrotic and weighed 0.041% of the body weight. Simultaneously, the weight of the right ventricle increased from 0.037 to 0.072% of the body weight. The hypertrophied right papillary muscle had a depressed force of contraction and prolonged contraction and relaxation phases. Angiotensin converting enzyme inhibition (ACEI) started early (24 h) prevented hypertrophy and normalized the contractile pattern under basic conditions. However, isoprenaline stimulation revealed that the relaxation phase was still prolonged. Concentration-effect curves for Ca2+ indicated that the pathological relaxation observed in the hypertrophied muscles and during isoprenaline stimulation of myocardium in ACEI treated animals could be due to insufficient re-uptake of cytosolic Ca2+ by the sarcoplasmic reticulum. The results support the idea that the development of right ventricular hypertrophy may contribute to pathophysiological consequences of an infarct in the left ventricle. ACEI started after 24 h prevented hypertrophy, whereas ACEI started after 14 days did not. ACEI was unable to normalize completely the balance between energy demand and energy delivery.

[The 24-hour heart rate variability. An important predictor of sudden death after myocardial infarction]

The activity of the cardiac autonomic nervous system can be estimated by measurement of beat to beat variations in heart rate-heart rate variability (HRV). In survivors after myocardial infarction, reduced 24-hour HRV, is an independent predictor of mortality/sudden cardiac death. The attenuated HRV is presumed to indicate reduced vagal function and concomitant high sympathetic activity. In experimental studies, this combination reduces the threshold for inducing malignant tachyarrhythmias, and is very probably a clinically important factor for the evolution of ventricular arrhythmias. Measurement of HRV in ordinary 24-hour ECG recordings can, together with other non-invasive measurements, stratify arrhythmic risk in survivors of myocardial infarction.

Atrial fibrillation and flutter after coronary artery bypass surgery: epidemiology, risk factors and preventive trials

Atrial fibrillation and atrial flutter are common arrhythmias after coronary artery bypass grafting. Although the consequences of the arrhythmia are generally not life-threatening, it constitutes a major clinical problem often requiring conversion to sinus rhythm. Atrial fibrillation or flutter can result in hypotension, heart failure, pneumonia, and stroke. This article reviews the literature on epidemiology, electrophysiology, risk factors, and preventive trials. The major conclusions are: (1) In patients undergoing coronary artery bypass surgery, the incidence of postoperative atrial fibrillation or flutter is 20-30%, the peak incidence being on the second or third postoperative day. (2) The strongest independent preoperative predictor for atrial fibrillation or flutter is the patients' age. (3) Intra-atrial conduction delay recorded pre and peroperatively may predict development of atrial fibrillation. (4) Peroperative inducibility of atrial fibrillation by pacing the right atrium may identify patients at risk for postoperative atrial fibrillation. (5) Development of postoperative atrial fibrillation or flutter has not been associated with peroperative or postoperative events. (6) The specificity and sensitivity of age and other possible relevant factors for prediction of atrial fibrillation or flutter after coronary artery bypass grafting is low. (7) No effective prophylactic regimen has yet been established.