Cardiovascular Outcomes Among Patients with Acute Coronary Syndromes and Diabetes: Results from ACS QUIK Trial in India

Background

Despite cardiovascular disease being the leading cause of death in India, limited data exist regarding the factors associated with outcomes in patients with diabetes who suffer acute myocardial infarction (AMI).

Methods

We examined 21,374 patients with AMI enrolled in the ACS QUIK trial. We compared in-hospital and 30-day major adverse cardiac events including death, re-infarction, stroke, or major bleeding in those with and without diabetes. The associations between diabetes and cardiac outcomes were adjusted for presentation and in-hospital management using logistic regression.

Results

Mean ± SD age was 60.1 ± 12.0 years, 24.3% were females, and 44.4% had diabetes. Those with diabetes were more likely to be older, female, hypertensive, and have higher Killip class but less likely to present with STEMI. Patients with diabetes had longer symptoms onset-to-arrival (median 225 vs 290 min; P < 0.001) and, in case of STEMI, longer door-to-balloon times (median, 75 vs 91 min; P < 0.001). Diabetes was independently associated with higher in-hospital death (adjusted odds ratio [aOR], 1.46; 95% CI, 1.12-1.89), in-hospital reinfarction (aOR, 1.52; 95% CI, 1.15-2.02), 30-day MACE (aOR, 1.33; 95% CI, 1.14-1.55) and 30-day death (aOR, 1.40; 95%CI, 1.16-1.69) but not 30-day stroke or 30-day major bleeding.

Conclusion

Among patients presenting with AMI in Kerala, India, a considerable proportion has diabetes and are at increased risk for in-hospital and 30-day adverse cardiovascular outcomes. Increased awareness of the increased cardiovascular risk and attention to the implementation of established cardiovascular therapies are indicated for patients with diabetes in lower-middle-income countries who develop AMI.

Clinical Trial registration

ClinicalTrials.gov Unique identifier: NCT02256658.

Higher HDL Cholesterol Levels Are Associated with Increased Markers of Interstitial Myocardial Fibrosis: Insights from The Multi-Ethnic Study of Atherosclerosis

Background

Emerging research indicates that high HDL-C levels might not be cardioprotective, potentially worsening cardiovascular disease(CVD)outcomes. Yet, there's no data on HDL-C's association with other CVD risk factors like myocardial fibrosis, a key aspect of cardiac remodeling predicting negative outcomes. We therefore aimed to study the association between HDL-C levels with interstitial myocardial fibrosis (IMF) and myocardial scar measured by CMR T1-mapping and late-gadolinium enhancement(LGE), respectively.

Methods

There were 1,863 participants (mean age of 69-years) who had both serum HDL-C measurements and underwent CMR. Analysis was done among those with available indices of interstitial fibrosis (extracellular volume fraction[ECV];N=1,172 and native-T1;N=1,863) and replacement fibrosis by LGE(N=1,172). HDL-C was analyzed as both logarithmically-transformed and categorized into <40 (low), 40-59 (normal), and ≥60mg/dL (high). Multivariable linear and logistic regression models were constructed to assess the associations of HDL-C with CMR-obtained measures of IMF, ECV% and native-T1 time, and myocardial scar, respectively.

Results

In the fully adjusted model, each 1-SD increment of log HDL-C was associated with a 1% increment in ECV%(p=0.01) and an 18-ms increment in native-T1(p<0.001). When stratified by HDL-C categories, those with high HDL-C(≥60mg/dL) had significantly higher ECV(β=0.5%,p=0.01) and native-T1(β =7ms,p=0.01) compared with those with normal HDL-C levels. Those with low HDL-C were not associated with IMF. Results remained unchanged after excluding individuals with a history of myocardial infarction. Neither increasing levels of HDL-C nor any HDL-C category was associated with the prevalence of myocardial scar.

Conclusions

Increasing levels of HDL-C were associated with increased markers of IMF, with those with high levels of HDL-C being linked to subclinical fibrosis in a community-based setting.

Aspirin for cardiovascular disease prevention among adults in the United States: Trends, prevalence, and participant characteristics associated with use

OBJECTIVE

: Aspirin has been widely utilized over several decades for atherosclerotic cardiovascular disease (ASCVD) prevention among adults in the United States. We examined trends in aspirin use among adults aged ≥40 years from 1998 to 2019 and assessed factors associated with its use for primary and secondary ASCVD prevention.

METHODS

: Using 1998-2019 Behavioral Risk Factor Surveillance System data, we obtained weighted prevalence of aspirin use among adults aged ≥40 years for each year and examined trends in use over this period. Using multivariable logistic regression and utilizing data from 54,388 respondents aged ≥40 years in the 2019 data, we assessed factors associated with aspirin use for secondary prevention and for primary prevention stratified by the number of traditional ASCVD risk factors reported (hypertension, diabetes mellitus, high cholesterol, overweight/obesity, and cigarette smoking).

RESULTS

: Aspirin use prevalence increased from 29.0%(95%CI, 27.9%-30.2%) in 1998 to 37.5%(36.9%-38.0%) in 2009. However, use has slightly declined over the last decade: 35.6%(34.6%-36.6%) in 2011 to 33.5%(32.5%-34.6%) in 2019. In 2019, among respondents without cardiovascular disease (CVD), 27.5%(26.4%-28.6%) reported primary prevention aspirin use while 69.7%(67.0%-72.2%) of respondents with CVD reported secondary prevention aspirin use. Of concern, 45.6%(43.5%-47.7%) of adults aged ≥70 years without CVD reported primary prevention aspirin use. Additionally, among individuals without any self-reported traditional ASCVD risk factor, males (adjusted odds ratio(aOR):1.60, 95%CI:1.12-2.27), persons aged ≥70 years (aOR:3.22, 95%CI:2.27-4.55), and individuals with healthcare coverage (aOR:2.28, 95%CI:1.17-4.44) had higher odds of primary prevention aspirin use compared to females, persons aged 40-69 years, and individuals without healthcare coverage, respectively. Females were less likely than males to report secondary prevention aspirin use (aOR:0.64, 95%CI:0.50-0.82).

CONCLUSION

: Aspirin use has slightly declined over the last decade. A significant proportion of adults aged ≥70 years reported primary prevention aspirin use in 2019. Since current guidelines do not recommend primary prevention aspirin use among adults aged ≥70 years, such use should be discouraged.

10-Year Resource Utilization and Costs for Cardiovascular Care

BACKGROUND

Cardiovascular disease (CVD) imparts a heavy economic burden on the U.S. health care system. Evidence regarding the long-term costs after comprehensive CVD screening is limited.

OBJECTIVES

This study calculated 10-year health care costs for 6,814 asymptomatic participants enrolled in MESA (Multi-Ethnic Study of Atherosclerosis), a registry sponsored by the National Heart, Lung, and Blood Institute, National Institutes of Health.

METHODS

Cumulative 10-year costs for CVD medications, office visits, diagnostic procedures, coronary revascularization, and hospitalizations were calculated from detailed follow-up data. Costs were derived by using Medicare nationwide and zip code-specific costs, inflation corrected, discounted at 3% per year, and presented in 2014 U.S. dollars.

RESULTS

Risk factor prevalence increased dramatically and, by 10 years, diabetes, hypertension, and dyslipidemia was reported in 19%, 57%, and 53%, respectively. Self-reported symptoms (i.e., chest pain or shortness of breath) were common (approximately 40% of enrollees). At 10 years, approximately one-third of enrollees reported having an echocardiogram or exercise test, whereas 7% underwent invasive coronary angiography. These utilization patterns resulted in 10-year health care costs of $23,142. The largest proportion of costs was associated with CVD medication use (78%). Approximately $2 of every $10 were spent for outpatient visits and diagnostic testing among the elderly, obese, those with a high-sensitivity C-reactive protein level >3 mg/l, or coronary artery calcium score (CACS) ≥400. Costs varied widely from <$7,700 for low-risk (Framingham risk score <6%, 0 CACS, and normal glucose measurements at baseline) to >$35,800 for high-risk (persons with diabetes, Framingham risk score ≥20%, or CACS ≥400) subgroups. Among high-risk enrollees, CVD costs accounted for $74 million of the $155 million consumed by MESA participants.

CONCLUSIONS

Longitudinal patterns of health care resource use after screening revealed new evidence on the economic burden of treatment and testing patterns not previously reported. Maintenance of a healthy population has the potential to markedly reduce the economic burden of CVD among asymptomatic individuals.

Thermal fatalities in Pretoria: A 5-year retrospective review

In South Africa, research on burn mortality has emanated primarily from specialised burn centres and has focused on specific age groups and hospital-based fatalities. This study describes the demographic profile and the pathology of trauma related to burn fatalities as seen at the Pretoria Medico-Legal Laboratory (PTA MLL), a large urban medico-legal mortuary over a 5-year period from January 2011 to December 2015. Mortuary admission records and autopsy reports were used to gather information on demographics, circumstances of injury, apparent manner and cause of death, pathology of burns, toxicology and histology reports and identification of the decedents. RESULTS: Of the 9558 unnatural deaths admitted to the PTA MLL during this time period, 291 (3.0%) of the fatalities met the inclusion criteria. The male:female ratio was 2.9:1. Most fatalities occurred between the ages of 0-4 years. One hundred and forty-two (142) decedents were charred beyond recognition. Identification was confirmed in 134 (94.4%) of the charred remains. In 208 (69.8%) of the cases the manner of death was deemed to be accidental, 23 (7.9%) were homicidal and 11 (3.8%) were suicides. Two hundred and fifty-five (87.4%) of the fatalities were as a result of open flames/fires. Shack fires were responsible for 105 (36%) of all fatalities. In 32 (11.0%) cases of open flame/fire fatalities where death occurred at the scene of injury, more than one fatality was reported per incident. In 122 (79.2%) of scene fatalities, soot deposition was noted in the upper and lower airways. Forty-five (32.8%) of hospital fatalities occurred within 24 h of admission. The most common complications in hospital fatalities were from the respiratory system. The mean blood alcohol concentrations (BAC) was 0.09 g/100 ml. The mean carboxyhaemoglobin concentrations (COHb) was 19.9%. All available cyanide results were negative. CONCLUSION: The study is the first of its kind in South Africa to generate bimodal descriptive statistics for burn fatalities. Approximately 3% of unnatural deaths at the PTA-MLL were due to burns, occurring at a rate of ±1 death per week. The data provides a platform for funding, collaborative research, planning and development of public health programs.

Abstract 031: Diastolic Blood Pressure, Coronary Artery Calcium, and Cardiac Outcomes in the Multi-ethnic Study of Atherosclerosis

Diastolic blood pressure (BP) has a J-curve relationship with coronary heart disease and death. Because this association is thought to reflect reduced coronary perfusion at low diastolic BP, our objective was to test whether the J-curve is most pronounced among persons with coronary artery calcium. Among 6,811 participants from the Multi-Ethnic Study of Atherosclerosis, we used Cox models to examine if diastolic BP category is associated with coronary heart disease events, stroke, and mortality. Analyses were conducted in the sample overall and after stratification by coronary artery calcium score. In multivariable-adjusted analyses, compared with diastolic BP of 80 to 89 mmHg (reference), persons with diastolic BP <60 mmHg had increased risk of coronary heart disease events (HR 1.69 [95% confidence interval 1.02-2.79]) and all-cause mortality (HR 1.48 [95% confidence interval 1.10-2.00]), but not stroke. After stratification, associations of diastolic BP <60 mmHg with events were present only among participants with coronary artery calcium >0. Diastolic BP <60 mmHg was not associated with events when coronary artery calcium was zero. We also found no interaction in the association between low diastolic BP and events based on race. In conclusion, diastolic blood pressure <60 mmHg was associated with increased risk of coronary heart disease events and all-cause mortality in the sample overall, but this association appeared strongest among individuals with elevated CAC; suggesting that added caution may be needed when pursuing intensive BP treatment targets among persons with subclinical atherosclerosis.

Interpretation of the evidence for the efficacy and safety of statin therapy

This Review is intended to help clinicians, patients, and the public make informed decisions about statin therapy for the prevention of heart attacks and strokes. It explains how the evidence that is available from randomised controlled trials yields reliable information about both the efficacy and safety of statin therapy. In addition, it discusses how claims that statins commonly cause adverse effects reflect a failure to recognise the limitations of other sources of evidence about the effects of treatment. Large-scale evidence from randomised trials shows that statin therapy reduces the risk of major vascular events (ie, coronary deaths or myocardial infarctions, strokes, and coronary revascularisation procedures) by about one-quarter for each mmol/L reduction in LDL cholesterol during each year (after the first) that it continues to be taken. The absolute benefits of statin therapy depend on an individual's absolute risk of occlusive vascular events and the absolute reduction in LDL cholesterol that is achieved. For example, lowering LDL cholesterol by 2 mmol/L (77 mg/dL) with an effective low-cost statin regimen (eg, atorvastatin 40 mg daily, costing about £2 per month) for 5 years in 10 000 patients would typically prevent major vascular events from occurring in about 1000 patients (ie, 10% absolute benefit) with pre-existing occlusive vascular disease (secondary prevention) and in 500 patients (ie, 5% absolute benefit) who are at increased risk but have not yet had a vascular event (primary prevention). Statin therapy has been shown to reduce vascular disease risk during each year it continues to be taken, so larger absolute benefits would accrue with more prolonged therapy, and these benefits persist long term. The only serious adverse events that have been shown to be caused by long-term statin therapy-ie, adverse effects of the statin-are myopathy (defined as muscle pain or weakness combined with large increases in blood concentrations of creatine kinase), new-onset diabetes mellitus, and, probably, haemorrhagic stroke. Typically, treatment of 10 000 patients for 5 years with an effective regimen (eg, atorvastatin 40 mg daily) would cause about 5 cases of myopathy (one of which might progress, if the statin therapy is not stopped, to the more severe condition of rhabdomyolysis), 50-100 new cases of diabetes, and 5-10 haemorrhagic strokes. However, any adverse impact of these side-effects on major vascular events has already been taken into account in the estimates of the absolute benefits. Statin therapy may cause symptomatic adverse events (eg, muscle pain or weakness) in up to about 50-100 patients (ie, 0·5-1·0% absolute harm) per 10 000 treated for 5 years. However, placebo-controlled randomised trials have shown definitively that almost all of the symptomatic adverse events that are attributed to statin therapy in routine practice are not actually caused by it (ie, they represent misattribution). The large-scale evidence available from randomised trials also indicates that it is unlikely that large absolute excesses in other serious adverse events still await discovery. Consequently, any further findings that emerge about the effects of statin therapy would not be expected to alter materially the balance of benefits and harms. It is, therefore, of concern that exaggerated claims about side-effect rates with statin therapy may be responsible for its under-use among individuals at increased risk of cardiovascular events. For, whereas the rare cases of myopathy and any muscle-related symptoms that are attributed to statin therapy generally resolve rapidly when treatment is stopped, the heart attacks or strokes that may occur if statin therapy is stopped unnecessarily can be devastating.

Sex Differences in Cardiovascular Disease Risk of Ghanaian- and Nigerian-Born West African Immigrants in the United States: The Afro-Cardiac Study

BACKGROUND

The number of African immigrants in the United States grew 40-fold between 1960 and 2007, from 35 355 to 1.4 million, with a large majority from West Africa. This study sought to examine the prevalence of cardiovascular disease (CVD) risk factors and global CVD risk and to identify independent predictors of increased CVD risk among West African immigrants in the United States.

METHODS AND RESULTS

This cross-sectional study assessed West African (Ghanaian and Nigerian) immigrants aged 35-74 years in the Baltimore-Washington metropolitan area. The mean age of participants was 49.5±9.2 years, and 58% were female. The majority (95%) had ≥1 of the 6 CVD risk factors. Smoking was least prevalent, and overweight or obesity was most prevalent, with 88% having a body mass index (in kg/m(2)) ≥25; 16% had a prior diagnosis of diabetes or had fasting blood glucose levels ≥126 mg/dL. In addition, 44% were physically inactive. Among women, employment and health insurance were associated with odds of 0.09 (95% CI 0.033-0.29) and 0.25 (95% CI 0.09-0.67), respectively, of having a Pooled Cohort Equations estimate ≥7.5% in the multivariable logistic regression analysis. Among men, higher social support was associated with 0.90 (95% CI 0.83-0.98) lower odds of having ≥3 CVD risk factors but not with having a Pooled Cohort Equations estimate ≥7.5%.

CONCLUSIONS

The prevalence of CVD risk factors among West African immigrants was particularly high. Being employed and having health insurance were associated with lower CVD risk in women, but only higher social support was associated with lower CVD risk in men.

Physical fitness and hypertension in a population at risk for cardiovascular disease: the Henry Ford ExercIse Testing (FIT) Project

BACKGROUND

Increased physical fitness is protective against cardiovascular disease. We hypothesized that increased fitness would be inversely associated with hypertension.

METHODS AND RESULTS

We examined the association of fitness with prevalent and incident hypertension in 57 284 participants from The Henry Ford ExercIse Testing (FIT) Project (1991–2009). Fitness was measured during a clinician‐referred treadmill stress test. Incident hypertension was defined as a new diagnosis of hypertension on 3 separate consecutive encounters derived from electronic medical records or administrative claims files. Analyses were performed with logistic regression or Cox proportional hazards models and were adjusted for hypertension risk factors. The mean age overall was 53 years, with 49% women and 29% black. Mean peak metabolic equivalents (METs) achieved was 9.2 (SD, 3.0). Fitness was inversely associated with prevalent hypertension even after adjustment (≥12 METs versus <6 METs; OR: 0.73; 95% CI: 0.67, 0.80). During a median follow‐up period of 4.4 years (interquartile range: 2.2 to 7.7 years), there were 8053 new cases of hypertension (36.4% of 22 109 participants without baseline hypertension). The unadjusted 5‐year cumulative incidences across categories of METs (<6, 6 to 9, 10 to 11, and ≥12) were 49%, 41%, 30%, and 21%. After adjustment, participants achieving ≥12 METs had a 20% lower risk of incident hypertension compared to participants achieving <6 METs (HR: 0.80; 95% CI: 0.72, 0.89). This relationship was preserved across strata of age, sex, race, obesity, resting blood pressure, and diabetes.

CONCLUSIONS

Higher fitness is associated with a lower probability of prevalent and incident hypertension independent of baseline risk factors.

Ten-year trends in coronary calcification in individuals without clinical cardiovascular disease in the multi-ethnic study of atherosclerosis

Background

Coronary heart disease (CHD) incidence has declined significantly in the US, as have levels of major coronary risk factors, including LDL-cholesterol, hypertension and smoking, but whether trends in subclinical atherosclerosis mirror these trends is not known.

Methods and Findings

To describe recent secular trends in subclinical atherosclerosis as measured by serial evaluations of coronary artery calcification (CAC) prevalence in a population over 10 years, we measured CAC using computed tomography (CT) and CHD risk factors in five serial cross-sectional samples of men and women from four race/ethnic groups, aged 55–84 and without clinical cardiovascular disease, who were members of Multi-Ethnic Study of Atherosclerosis (MESA) cohort from 2000 to 2012. Sample sizes ranged from 1062 to 4837. After adjusting for age, gender, and CT scanner, the prevalence of CAC increased across exams among African Americans, whose prevalence of CAC was 52.4% in 2000–02, 50.4% in 2003–04, 60.0% is 2005–06, 57.4% in 2007–08, and 61.3% in 2010–12 (p for trend <0.001). The trend was strongest among African Americans aged 55–64 [prevalence ratio for 2010–12 vs. 2000–02, 1.59 (95% confidence interval 1.06, 2.39); p = 0.005 for trend across exams]. There were no consistent trends in any other ethnic group. Risk factors generally improved in the cohort, and adjustment for risk factors did not change trends in CAC prevalence.

Conclusions

There was a significant secular trend towards increased prevalence of CAC over 10 years among African Americans and no change in three other ethnic groups. Trends did not reflect concurrent general improvement in risk factors. The trend towards a higher prevalence of CAC in African Americans suggests that CHD risk in this population is not improving relative to other groups.

C-reactive protein is independently associated with coronary atherosclerosis burden among octogenarians

AIM OF THE STUDY

In contrast to the general population, individuals with primarily persistent elevation of inflammatory activity display a significant association between inflammatory biomarkers and atherosclerotic burden. In older individuals, immunosenescence upregulates the innate response and, by this way, may hypothetically favor the presence of this association. The aim of this study was to evaluate this hypothesis in healthy octogenarians.

METHODS

Participants (n = 208) aged 80 years or older, asymptomatic and without medical and laboratory evidence of chronic diseases or use of anti-inflammatory treatments were included in the study. Lipid profile and plasma C-reactive protein (CRP) were measured at baseline and cardiac computed tomography was performed within 1-week interval for measuring coronary calcium score (CCS).

RESULTS

The median plasma CRP was 1.9 mg/L (1.0–3.4) and 33 % of the participants had elevated CRP defined as C3 mg/L. Among those with high CRP, there was an increased frequency of high CCS (C100) as compared with their counterparts (71 vs 50 %, p = 0.001). The association between CRP and CCS persisted even after adjustment for age, sex, cardiovascular risk factors and statin therapy. The area under the receiver-operating curve for CRP was 0.606 using CCS C100 as a binary outcome. The sensitivities for CCS C100 were 40 and 74 % for the cutoff points of CRP C3 or 1 mg/L, respectively.

CONCLUSION

The present study was able to confirm that in very elderly individuals, systemic inflammatory activity is independently associated with coronary atherosclerosis burden.

The prevalence of the metabolically healthy obese phenotype in an aging population and its association with subclinical cardiovascular disease: The Brazilian study on healthy aging

BACKGROUND

Current literature has elucidated a new phenotype, metabolically healthy obese (MHO), with risks of cardiovascular disease similar to that of normal weight individuals. Few studies have examined the MHO phenotype in an aging population, especially in association with subclinical CVD.

RESEARCH DESIGN AND METHODS

This cross sectional study population consisted of 208 octogenarians and older. Anthropometrics, biochemical, and radiological parameters were measured to assess obesity, metabolic health (assessed by the National Cholesterol Education Program -Adult Treatment Panel (NCEP-ATP III) criteria), and subclinical measures of CVD.

RESULTS

The prevalence of MHO was 13.5% (N = 28). No significant association with MHO was noted for age, coronary artery calcium score, cIMT, or hs-CRP > 3 mg/dl (p = NS).

CONCLUSIONS

Our results suggest that the MHO phenotype exists in the elderly; however, subclinical CVD measures were not different in sub-group analysis suggesting traditional metabolic risk factor algorithms may not be accurate in the very elderly.

Relation of hepatic steatosis to atherogenic dyslipidemia

Hepatic steatosis is closely associated with the metabolic syndrome. We assessed for an independent association between hepatic steatosis and atherogenic dyslipidemia after adjustment for obesity, physical activity, hyperglycemia, and systemic inflammation. We studied 6,333 asymptomatic subjects without clinical cardiovascular disease undergoing a health screen in Brazil from November 2008 to July 2010. Hepatic steatosis was diagnosed by ultrasound. Atherogenic dyslipidemia was defined using 2 definitions: criteria for (1) metabolic syndrome or (2) insulin resistance (triglyceride/high-density-lipoprotein cholesterol ratio of ≥2.5 in women and ≥3.5 in men). In hierarchical multivariate regression models, we evaluated for an independent association of hepatic steatosis with atherogenic dyslipidemia. Hepatic steatosis was detected in 36% of participants (average age 43.5 years, 79% men, average body mass index 26.3 kg/m(2)). Subjects with hepatic steatosis had similar levels of low-density-lipoprotein cholesterol, with significantly lower level of high-density-lipoprotein cholesterol and higher level of triglyceride compared with those without steatosis. Hepatic steatosis remained significantly independently associated with atherogenic dyslipidemia of both definitions (metabolic syndrome [odds ratio 2.47, 95% confidence interval 2.03 to 3.02] and insulin resistance [odds ratio 2.50, 95% confidence interval 2.13 to 2.91]) after multivariate adjustment. Stratified analyses showed a persistent independent association in nonobese subjects, those without metabolic syndrome, those with normal high-sensitivity C-reactive protein, nonalcohol abusers, and those with normal liver enzymes. Hepatic steatosis was significantly associated with atherogenic dyslipidemia independent of obesity, physical activity, hyperglycemia, and systemic inflammation after multivariate adjustment. In conclusion, this adds to the growing body of evidence that hepatic steatosis may play a direct metabolic role in conferring increased cardiovascular risk.

Membrane excitability and dissipative instabilities

Electrical excitation is interpreted in terms of a cooperative structural transition of membrane protomers coupled with the translocation of a permeant molecule in a non-equilibrium environment. Equations for flow of permeant and for membrane conformation are derived for the simple case of a single non-charged permeant. On the basis of a few simple physical assumptions, the theory predicts several important properties of electrically excitable membranes: the steepness of the relation between membrane conductance and potential, the presence of a negative conductance, and the occurrence of instabilities following rapid perturbations of membrane environment, giving rise to some simple cases of action potentials. Several experimental tests of the membrane with its changes of electrical properties are proposed. From a thermodynamic point of view, an electrically excitable membrane, in its resting state, lies beyond a dissipative instability and consequently is in a non-equilibrium state but with stable organization, a "dissipative structure" of Prigogine. Membrane excitation following a small perturbation of the environment would correspond to a jump from such an organization to another stable organization but close to thermodynamic equilibrium. It is shown how the cooperative molecular properties of the membrane are amplified by energy dissipation at the macroscopic level.