Effect of primary coronary intervention on heart rate variability and left ventricular function in patients with acute myocardial infarction

AIM

Several studies showed that primary percutaneous coronary interventions (PCI) have a favourable impact on left ventricular remodeling and heart rate variability (HRV) both at short- and long-term follow-up in patients suffering an acute myocardial infarction (AMI). However, no previous study investigated the relationship between left ventricular remodeling and changes in HRV during follow-up in AMI patients treated by primary PCI.

METHODS

We studied 28 patients with AMI (57+/-8 years, 27 men), treated by PCI within 12 hours of symptom onset. Patients underwent a 24-hour ECG Holter recording and left ventricular ejection fraction (LVEF) echocardiographic assessment before discharge, and at 1-month and 6-month follow-up. HRV was measured in the time- and frequency-domain.

RESULTS

A significant improvement of both time- and frequency-domain HRV variables was observed at 1-month and at 6-month follow-up with the most significant changes being found for standard deviation of normal-normal beat intervals (SDNN) in the time-domain (95.5+/-26.1 ms vs 125.5+/-29.8 ms vs 142.8+/-28.8 ms, respectively; P<0.001) and for very low frequency (VLF) amplitude in the frequency-domain (36.7+/-9.8 ms vs 44.1+/-11.1 vs 48.9+/-12.2 ms, respectively; P<0.001). In contrast, compared to basal values, LVEF was substantially unchanged at 1-month and 6-month follow-up (48.8+/-8.5% vs 50.8+/-10% vs 49.6+/-9%, respectively; P=0.25). At 6-month follow-up 11 patients showed an improvement of >or= 5% of LVEF, whereas 17 patients did not show any improvement of LVEF. HRV variables significantly improved in a similar way in these two subgroups both at 1-month and at 6-month follow-up.

CONCLUSION

Our data demonstrate that, in AMI patients treated by primary PCI, HRV improves over time, independent of changes in LVEF. The clinical implications of these findings deserve to be addressed in future studies.

Exercise-induced ST-segment elevation in patients with a recent acute myocardial infarction treated by primary percutaneous coronary intervention

OBJECTIVES

To get insight in the mechanism of exercise-induced ST-segment elevation (STE) in patients with Q/QS waves at the electrocardiogram (ECG).

METHODS

We performed exercise stress test in 13 patients with anterior acute myocardial infarction treated by successful primary percutaneous coronary intervention (PCI).

RESULTS

Compared to rest, an additional STE > or = 1 mm in one or more precordial ECG leads during exercise occurred in nine patients (69%), in the absence of symptoms.

CONCLUSIONS

In acute myocardial infarction (MI) patients, treated by primary PCI and showing optimal coronary blood flow restoration at angiography, STE can still be induced by exercise in Q/QS wave ECG leads. This finding lends further support to the theory that exercise-induced STE in this clinical context is unlikely to represent by itself transient myocardial ischemia or viability.

Cardiac magnetic resonance of healthy children and young adults with frequent premature ventricular complexes

OBJECTIVE

To assess whether magnetic resonance imaging could detect any cardiac morphological or functional myocardial alterations in healthy children and young adults with ventricular arrhythmias.

METHODS

Twenty-three subjects (14 male, mean age 15.6 +/- 6.5 years) with frequent (> or =30/h) premature ventricular complexes (PVCs) on Holter monitoring and normal echocardiographic and electrocardiographic findings underwent cardiac magnetic resonance (CMR) on a 1.5T scanner and an exercise stress test. Subjects were also followed up for a period of 71 +/- 24 months.

RESULTS

CMR showed no evidence of structural cardiac abnormalities, but functional assessment revealed significant impairment in 17 subjects (74%): mild to moderate right ventricular enlargement was found in all of these subjects associated with a mild reduction of ventricular function in five cases (22%) and mild free wall and/or apex contraction abnormalities in eight subjects (35%). PVCs persisted during stress test in three subjects (13%) and disappeared in 19 (83%). No serious cardiac event was observed during the follow-up.

CONCLUSIONS

Our study shows that subjects with PVCs without detectable electrocardiographic and echocardiographic abnormalities frequently exhibit functional impairment of the right ventricle at CMR, potentially responsible for ventricular arrhythmias. Although the causes of these abnormalities remain to be elucidated, the long-term outcome of these subjects is excellent.

The complex link between oxidised low-density lipoprotein and unstable angina

OBJECTIVE

The role of oxidised low-density lipoprotein (ox-LDL) in plaque destabilisation is controversial; therefore we aimed at comparing plaque and plasma ox-LDL content in stable and unstable ischaemic syndromes. We also assessed the correlation between plaque or plasma ox-LDL and angiographic complex stenosis morphology.

METHODS

Ten consecutive patients with chronic stable angina (SA) and 10 consecutive patients with unstable angina (UA) were studied. Plaque sections obtained by directional coronary atherectomy were immunostained with the monoclonal antibody mAb-4E6, which recognises several oxidation epitopes on LDL (mAb-4E6 ox-LDL), and with the monoclonal antibody mAb-1H11 (mAb-1H11 ox-LDL), which recognises malondialdehyde-modified LDL. An mAb-4E6-based competition ELISA was used for quantification of ox-LDL in plasma. C-reactive protein serum levels were measured by a high-sensitivity nephelometric assay. An angiographic analysis was performed to assess severity and extent of coronary atherosclerotic disease and stenosis morphology.

RESULTS

Percent plaque area occupied by mAb-4E6 ox-LDL or mAb-1H11 ox-LDL was similar in patients with SA or UA (22.4 +/- 13.1 vs. 21.1 +/- 19.7%, P = 0.8 and 19.3 +/- 10.4 vs. 16.8 +/- 16.9%, P = 0.6, respectively), whereas ox-LDL plasma levels were significantly higher in patients with UA than in patients with SA (2.4 +/- 1.1 vs. 0.9 +/- 0.6 mg/dl; P = 0.03). Furthermore, a significant correlation was found between plasma levels of ox-LDL and the number of angiographically complex lesions (P = 0.03) or C-reactive protein serum levels (P = 0.04).

CONCLUSIONS

Neither plaque mAb-4E6 ox-LDL nor plaque mAb-1H11 ox-LDL seem to be a major trigger of coronary plaque instability. However, circulating ox-LDL might be involved in plaque vulnerability and coronary artery disease activity.

Relationship between changes in platelet reactivity and changes in platelet receptor expression induced by physical exercise

INTRODUCTION

In previous studies we have consistently shown a significant increase of platelet reactivity after exercise in patients with obstructive coronary artery disease (CAD). We also observed a significant individual variability in the response to exercise of platelet reactivity in these patients. Whether exercise-induced changes in platelet reactivity correlate with changes in platelet membrane receptors in patients with CAD is unknown.

METHODS

We studied 26 patients with stable CAD and 10 matched healthy controls who underwent a symptom-limited treadmill exercise stress test. Venous blood samples were collected at rest and within 5 min of peak exercise. Platelet reactivity was measured by the PFA-100 method as time to occlude (closure time, CT) a ring coated with collagen/adenosine diphosphate (C/ADP). Platelet expression of glycoprotein (GP) IIb/IIIa, in both global (CD41) and active form (PAC-1), and P-selectin (CD62P) and formation of leukocyte-platelet aggregates were assessed by flow cytometry.

RESULTS

After exercise CT did not change in controls (85.4+/-12 to 84.0+/-9 s, p=0.37), whereas it decreased in CAD patients (98.8+/-24 to 91.4+/-25 s, p<0.001). After exercise, CD41 and PAC-1 platelet expression increased significantly in CAD patients (p=0.04 for both), but not in controls (p=0.39 and p=0.98, respectively). To evaluate the relationship between the response to exercise of platelet reactivity and of platelet receptor expression, CAD patients were divided into two groups: CAD group 1 (16 patients, decrease in CT >5 s after exercise) and CAD group 2 (10 patients no increase in platelet reactivity after exercise). CD41 and PAC-1 expression increased in CAD group 1 (p=0.008 and p=0.026, respectively) but not in CAD group 2 (p=0.39 and p=0.50, respectively). No significant differences were observed between the 2 groups for changes in CD62P and leukocyte-platelet aggregates.

CONCLUSIONS

Our data show that, in patients with stable CAD, an increased platelet reactivity to C/ADP stimulation after exercise, as assessed by the PFA-100 method, is specifically associated with an increased expression of platelet GP IIb/IIIa receptor.

Effect of vagal nerve stimulation on systemic inflammation and cardiac autonomic function in patients with refractory epilepsy

OBJECTIVE

Recent data suggest that vagus nerve stimulation (VNS) can inhibit cytokine release by inflammatory cells. Accordingly, an association between impaired cardiac parasympathetic function, as assessed by heart rate variability (HRV), and increased markers of inflammation has recently been reported. In this study we assessed the effect of direct left VNS on inflammatory markers and HRV in patients with refractory epilepsy.

METHODS

A 24-hour electrocardiogram Holter recording was performed both at baseline and after 3 months of left VNS in 8 patients (age 32 +/- 24 years, 2 men) who underwent implantation of a VNS device because of refractory epilepsy. Tumor necrosis factor-alpha, interleukin-6 and C-reactive protein serum levels were measured, as markers of inflammation, at the same times.

RESULTS

No significant changes were found after 3 months of left VNS, compared to baseline, both for HRV variables and inflammatory markers. Also, no consistent correlation could be demonstrated between HRV parameters and inflammatory markers in these patients.

CONCLUSIONS

Our data in epileptic patients without cardiovascular disease failed to show a significant effect of left VNS on cardiac autonomic function and on systemic inflammation at short-term follow-up.

Inflammatory predictors of mortality in the Scandinavian Simvastatin Survival Study

BACKGROUND AND HYPOTHESIS

The predictive value of specific markers of infection and autoimmunity for coronary events, such as the effects of statins on inflammation, is still controversial.

METHODS

A case-control design was used to compare C-reactive protein (CRP) levels, seropositivity for Chlamydia pneumoniae and Helicobacter pylori, and anti-oxidized low-density lipoprotein (oxLDL) antibody levels in prerandomization blood samples from 129 participants in the Scandinavian Simvastatin Survival Study who died (cases), and from 129 matched participants who were alive during 5-year follow-up (controls).

RESULTS

Patients with CRP levels in the highest quartile had an increased risk of death compared with those in the first through third quartile (odds ratio [OR] = 2.51, 95% confidence interval [CI] 1.3-4.8). Seropositivity for Chlamydia pneumoniae or Helicobacter pylori and anti-oxLDL antibody levels were similar in cases and controls (p = NS). At a 4-month control, simvastatin reduced CRP levels (p = 0.009) while placebo did not (p = NS). However, the risk of death associated with high baseline CRP levels was similar in patients randomized to placebo (OR = 2.36, 95% CI 1.06-5.26) or simvastatin (OR = 3.13, 95% CI 1.06-9.21).

CONCLUSIONS

Elevated CRP levels, but not seropositivity for Chlamydia pneumoniae or Helicobacter pylori, nor levels of anti-oxLDL antibodies, predict the risk of death in patients with stable ischemic heart disease. Simvastatin treatment reduces CRP levels, but without affecting the increased risk conferred by higher CRP levels at baseline.

Heart Rate Turbulence as a Noninvasive Risk Predictor of Ventricular Tachyarrhythmias in Myotonic Dystrophy Type 1

INTRODUCTION

Myotonic dystrophy type 1 (MD1) is the most common muscular dystrophy of adult life. Cardiac involvement is characterized by disorders of atrioventricular conduction, ventricular arrhythmias, and sudden death. Heart rate turbulence (HRT) is a noninvasive risk predictor in patients affected by ischemic heart disease. The aim of our study is to assess the prognostic value of HRT in MD1 patients.

METHODS AND RESULTS

We performed HRT analysis by 24-hour Holter recording to calculate turbulence onset (TO) and turbulence slope (TS) in 29 MD1 patients (mean age 52 +/- 10 years), and in 30 patients (mean age 52 +/- 13 years) with frequent ventricular arrhythmias and structurally normal heart (VANH). An electrophysiological study (EPS) tested ventricular arrhythmias inducibility in 22 MD1 patients. TO was significantly different between MD1 and VANH patients (-1.66 +/- 2.04 and -2.98 +/- 1.79%, respectively, P 0.01), while no difference was observed in TS between MD1 and VANH patients (11.12 +/- 6.46 and 9.12 +/- 6 msec/beat, respectively). On EPS, sustained ventricular arrhythmias (SVA) were induced in six MD1 patients. TO was significantly different in inducible MD1 patients (0.88 +/- 1.95%), as compared with both noninducible (-2.49 +/- 1.43%, P < 0.001) or no eligible to EPS (-1.93 +/- 1.63%, P < 0.005) MD1 patients and to VANH patients (-2.98 +/- 1.79%, P < 0.001).

CONCLUSIONS

An impairment of TO, a measure of HRT, suggesting impaired cardiac parasympathetic activity, may be a useful, noninvasive predictor of arrhythmic risk in MD1 patients.

Baseline systemic inflammatory status and no-reflow phenomenon after percutaneous coronary angioplasty for acute myocardial infarction

BACKGROUND

Systemic inflammation is involved in several pathological cardiovascular processes. However, whether it plays a role in the no-reflow phenomenon occurring in patients with acute myocardial infarction (AMI) after percutaneous coronary intervention (PCI) is unknown.

METHODS

We studies 60 consecutive patients (59.5+/-12 years, 82% males) with a first ST-segment elevation AMI, treated by primary or rescue PCI within 6 h of symptom onset. Angiographic indexes of no-reflow, evaluated at the end of the procedure, included coronary TIMI flow grading, corrected TIMI frame count (c-TFC) and myocardial blush grade (MBG). ECG indexes of no-reflow included the lack of ST segment resolution (defined as a reduction <50% of the measured ST-segment elevation at 90 min, compared to the admission ECG), as analyzed both in the single lead with the maximal ST elevation and in all leads showing ST elevation on admission. Patients were divided into two groups according to baseline high-sensitivity C-reactive protein (CRP) serum levels measured on admission: high CRP group (CRP>5 mg/L) and low CRP group (CRP<5 mg/L).

RESULTS

A similar prevalence of final TIMI flow<3 and MBG<3 was observed in patients with high and low CRP serum levels (30% vs. 12%, p=0.1, and 50% vs. 53%, p=1.0, respectively), and c-TFC was also similar in the two groups (26+/-4.5 vs. 24+/-6, p=0.5). Accordingly, the prevalence of lack of ST-segment resolution in the two groups was similar, both by the single-lead method (25% vs. 25%, p=1.0) and the multiple-lead method (29% vs. 19%, p=0.4).

CONCLUSION

In this study we failed to demonstrate any significant association between CRP serum levels on admission and coronary no-reflow, as assessed by both angiographic and ECG parameters in AMI patients treated by successful primary or rescue PCI within 6 h of chest pain onset.

Relation of heart rate variability to serum levels of C-reactive protein in patients with unstable angina pectoris

Heart rate variability (HRV) and systemic markers of inflammation have prognostic value in patients with unstable angina pectoris (UAP). However, it is unknown whether any relation exists between HRV parameters and indexes of inflammation in this clinical context. We assessed HRV on 24-hour electrocardiographic Holter recordings, performed within 24 hours of admission, and measured C-reactive protein (CRP) serum levels by a high-sensitivity assay on admission, in 531 patients with UAP (65+/-10 years of age; 347 men) who were enrolled in the prospective multicenter study Stratificazione Prognostica dell'Angina Instabile (SPAI). A significant inverse correlation was found between CRP levels and all HRV parameters, with the highest r coefficient shown with SD of all RR intervals (r= -0.23; p<0.001) in the time domain and with very low-frequency amplitude (r= -0.22; p<0.001) in the frequency domain. When patients were categorized into 4 groups according to CRP quartile levels, statistically significant lower HRV values were observed in the upper CRP quartile. On separate multiple regression analyses, including the most important clinical and laboratory variables, SD of all RR intervals and very low-frequency amplitude were the most significant predictors of increasing CRP levels (p<0.001 for the 2 comparisons). In contrast, in models with SD of all RR intervals and very low-frequency amplitude as dependent variables, CRP was a strong predictor of impaired cardiac autonomic function (p<0.001 for the 2 comparisons). Thus, our data show that, in patients with UAP, high levels of serum CRP levels are significantly associated with decreased HRV, suggesting a possible pathophysiologic link between cardiac autonomic dysfunction and inflammatory activity.

Cardiac syndrome X: a critical overview and future perspectives

The classic definition of cardiac syndrome X (CSX) seems inadequate both for clinical and research purposes and should be replaced with one aimed at including a sufficiently homogeneous group of patients with the common plausible pathophysiological mechanism of coronary microvascular dysfunction. More specifically, CSX should be defined as a form of stable effort angina, which, according to careful diagnostic investigation, can reasonably be attributed to abnormalities in the coronary microvascular circulation.

Prognostic value of ventricular arrhythmias and heart rate variability in patients with unstable angina

OBJECTIVES

To assess the prognostic value of ventricular arrhythmias (VA) and heart rate variability (HRV) in patients with unstable angina.

DESIGN

Multicentre prospective study.

SETTING

17 cardiological centres in Italy.

PATIENTS

543 consecutive patients with unstable angina and preserved left ventricular function (ejection fraction >or=40%) enrolled in the SPAI (Stratificazione Prognostica dell'Angina Instabile) study.

METHODS

Patients underwent 24 h ECG Holter monitoring within 24 h of hospital admission. Tested variables were frequent ventricular extrasystoles (>or=10/h), complex (that is, frequent or repetitive) VA, and bottom quartile values of time-domain and frequency-domain HRV variables. Primary end points were in-hospital and six-month total and cardiac deaths.

RESULTS

Eight patients died in hospital (1.5%) and 32 (5.9%, 29 cardiac) during follow up. Both complex VA and frequent extrasystoles were strongly predictive of death in hospital and at follow up, even after adjustment for clinical (age, sex, cardiac risk factors and history of myocardial infarction) and laboratory (troponin I, C reactive protein and transient myocardial ischaemia on Holter monitoring) variables. At univariate analysis bottom quartile values of three HRV variables (standard deviation of RR intervals index, low-frequency amplitude and low to high frequency ratio) were associated with in-hospital death, and bottom quartile values of most HRV variables predicted six-month fatal events. At multivariate Cox survival analysis reduced low-frequency amplitude was consistently found to be independently associated with fatal end points.

CONCLUSION

In patients with unstable angina with preserved myocardial function, both VA and HRV are independent predictors of in-hospital and medium-term mortality, suggesting that these factors should be taken into account in the risk stratification of these patients.

Effect of primary percutaneous coronary intervention versus thrombolysis on ventricular arrhythmias and heart rate variability in acute myocardial infarction

BACKGROUND

Several studies showed that thrombolysis reduces ventricular arrhythmias and improves heart rate variability (HRV) in patients with acute myocardial infarction (AMI). Primary percutaneous coronary intervention (PCI) has recently become the treatment of choice for AMI, but it is still unknown whether it has favorable effects on these prognostic variables.

METHODS

We studied a group of 44 consecutive AMI patients (39 males, 5 females, mean age 59 +/- 9 years) submitted to primary PCI and 93 consecutive AMI patients (80 males, 13 females, mean age 61.0 +/- 11 years) treated with thrombolytic therapy within 6 hours of symptom onset. All patients underwent 24-hour Holter recording before discharge.

RESULTS

The number of premature ventricular beats and the prevalence of non-sustained ventricular tachycardia in the 24 hours were lower in the PCI group (162 +/- 474 and 9%, respectively) than in the thrombolysed group (334 +/- 1730 and 14%, respectively), but the difference did not achieve statistical significance (p = 0.62 and p = 0.58, respectively). There were also no significant differences in HRV variables between the two groups, although a lower proportion of PCI patients tended to have bottom quartile values of HRV variables. The favorable trend for arrhythmias and HRV in PCI patients, however, seemed to be related to a worse basal clinical profile of thrombolysed patients, including a higher prevalence of previous AMI (14 vs 2%, p = 0.065), diabetes (27 vs 18%, p = 0.14) and, in particular, a lower use of beta-blockers (35 vs 93%, p < 0.001).

CONCLUSIONS

In this study, we failed to show any significant benefit of primary PCI compared to thrombolysis on ventricular arrhythmias and HRV in patients with ST-segment elevation AMI. The clinical implications of these findings deserve investigation in future studies.

Mobilization of bone marrow-derived stem cells after myocardial infarction and left ventricular function

AIMS

Recent data suggest that the administration of bone marrow-derived stem cells (BMSC) might improve myocardial perfusion and left ventricular (LV) function after acute myocardial infarction (AMI). The aim of this study was to assess spontaneous mobilization of BMSC expressing the haematopoietic and endothelial progenitor cell-associated antigen CD34+ after AMI and its relation to post-infarction remodelling.

METHODS AND RESULTS

Peripheral blood concentration of CD34+ BMSC was measured by flow cytometry in 54 patients with AMI, 26 patients with chronic stable angina (CSA), and 43 normal healthy subjects. In patients with AMI, LV function was measured by 2D-echocardiography. Eighteen AMI patients were reassessed at 1 year. BMSC concentration was higher in patients with AMI (mean peak value: 7.04+/-6.27 cells/microL), than in patients with CSA (3.80+/-2.12 cells/microL, P=0.036) and in healthy controls (1.87+/-1.52 cells/microL, P<0.001). At multivariable analysis statin use (P<0.001), primary percutaneous intervention (P=0.048) and anterior AMI (P=0.05) were the only independent predictors of increased BMSC mobilization after AMI. In the 28 patients without subsequent acute coronary events reassessed at 1 year follow-up, CD34+ cell concentration was an independent predictor of global and regional improvement of LV function (r=0.52, P=0.004 and r=-0.41, P=0.03, respectively).

CONCLUSION

AMI is followed by enhanced spontaneous mobilization of BMSC, in particular, in patients on statin therapy and following a primary percutaneous intervention. More importantly persistent spontaneous mobilization of BMSC might contribute to determine a more favourable post-AMI remodelling.

Effect of spinal cord stimulation on spontaneous and stress-induced angina and 'ischemia-like' ST-segment depression in patients with cardiac syndrome X

AIMS

A significant number of patients with cardiac syndrome X (CSX) present frequent episodes of severe chest pain, refractory to maximal multi-drug therapy. A few, small, uncontrolled data suggested that spinal cord stimulation (SCS) may have favourable clinical benefits in these patients.

METHODS AND RESULTS

We studied 10 CSX patients who were being treated by SCS for refractory angina pectoris for 17+/-16 months (median 8). Patients were randomized to either continue or withdraw SCS for a period of 3 weeks and were then crossed over to the other condition for a further 3-week period. During each 3-week period patients kept a detailed diary of angina episodes occurring in the last 2 weeks of each phase. Furthermore, at the end of each 3-week period, angina status was also assessed by Seattle Angina Questionnaire (SAQ), a 0-100 visual analogue scale (VAS), and patients underwent 24-h Holter monitoring (HM) and echocardiographic dobutamine stress test (DST). Compared with the withdrawal phase, SCS reduced the number (P=0.01), duration (P=0.022), and severity (P=0.011) of angina episodes, and nitrate consumption (P=0.042). SAQ scores (P< or =0.013 for all) and VAS (P<0.001) were also improved, the number of episodes of ST-segment depression on HM was decreased (P=0.014), and time to angina (P=0.045) and to 1 mm ST-segment depression (P=0.04) during DST were both prolonged by SCS.

CONCLUSIONS

Our data point out that SCS may be an effective form of treatment in patients with CSX suffering from frequent angina episodes significantly impairing quality of life (QOL) and refractory to maximally tolerated drug therapy.

Diagnostic and prognostic value of ST segment depression limited to the recovery phase of exercise stress test

OBJECTIVES

To investigate the diagnostic and prognostic value of ST segment depression limited to the recovery phase of an exercise stress test, as compared with that of ST segment depression appearing during exercise.

SETTING

Exercise stress test laboratory of a university hospital.

PATIENTS AND DESIGN

Clinical and angiographic data were compared for 574 consecutive patients who developed ST segment depression during the active phase of an exercise test (group 1) and for 79 patients who developed ST segment depression only during the recovery phase of the exercise test (group 2).

RESULTS

There were no differences between the two groups in major clinical features. Significant coronary artery stenoses were found in 488 group 1 patients (85%) and in 62 group 2 patients (78%, p = 0.14). Three vessel or left main disease was found in 166 (29%) group 1 and in 14 (18%) group 2 patients (p = 0.045). At a median follow up of 55.3 months of 321 group 1 and 54 group 2 patients, there were no significant differences in major cardiac events between the groups (univariate relative risk 0.81, 95% confidence interval 0.25 to 2.68, p = 0.72).

CONCLUSION

The diagnostic and prognostic power of ST segment depression limited to the recovery phase of an exercise test is largely similar to that of ST segment depression induced during effort; thus, assessing ST segment depression during recovery can significantly improve the clinical information derived from exercise stress tests.

Ethnic variations in acute coronary syndromes

Although it is very likely that ethnic variations in the incidence and, possibly, clinical outcome of acute coronary artery disease events exist, the causes for such differences are many and difficult to address fully, given the complex interplay of contributing factors.

Sex, survival bias, and mortality following acute myocardial infarction

Several though not all studies have found an up to 2-fold increase in 30-day mortality in women compared to men admitted to hospital for ST-elevation myocardial infarction (MI), even after adjustment for baseline variables. These data however do not take into account the pre-hospital period. Indeed, three large WHO MONICA reports that included out-of-hospital events found no significant gender difference in overall 28-day mortality from MI, with more men dying before reaching the hospital (presumably of ventricular tachyarrhythmias) and more women dying after hospital admission (presumably of heart failure). Women compared to men exhibit enhanced vagal activity, both under basal conditions and during angioplasty-induced coronary occlusion, and this may afford protection against malignant ventricular arrhythmias. Epidemiological data indicate that women dying of ischemic heart disease are less prone to sudden death than men. Taken together, the above findings suggest that, following acute MI, significant gender differences lie not so much in overall mortality, but in the timing and mechanisms of death.