Does stopping smoking delay onset of angina after infarction?

Smoking cessation for secondary prevention of cardiovascular disease

BACKGROUND

Smoking is a leading cause of cardiovascular disease (CVD), particularly coronary heart disease (CHD). However, quitting smoking may prevent secondary CVD events in people already diagnosed with CHD.  OBJECTIVES: To examine the impact of smoking cessation on death from CVD and major adverse cardiovascular events (MACE), in people with incident CHD.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group's Specialised Register, CENTRAL, MEDLINE, Embase, Cumulative Index to Nursing and Allied Health Literature, and the trials registries clinicaltrials.gov and the International Clinical Trials Registry Platform. We ran all searches from database inception to 15 April 2021.  SELECTION CRITERIA: We included cohort studies, and both cluster- and individually randomised controlled trials of at least six months' duration. We treated all included studies as cohort studies and analysed them by smoking status at follow-up. Eligible studies had to recruit adults (> 18 years) with diagnosed CHD and who smoked tobacco at diagnosis, and assess whether they quit or continued smoking during the study. Studies had to measure at least one of our included outcomes with at least six months' follow-up. Our primary outcomes were death from CVD and MACE. Secondary outcomes included all-cause mortality, non-fatal myocardial infarction, non-fatal stroke, new-onset angina and change in quality of life.  DATA COLLECTION AND ANALYSIS: We followed standard Cochrane methods for screening and data extraction.  We assessed the risk of bias for the primary outcomes using the ROBINS-I tool. We compared the incidence of death from CVD and of MACE (primary outcomes) between participants who quit smoking versus those who continued to smoke for each included study that reported these outcomes. We also assessed differences in all-cause mortality, incidence of non-fatal myocardial infarction, incidence of non-fatal stroke and new onset angina. We calculated hazard ratios (HRs) and 95% confidence intervals (95% CI). For our outcome, change in quality of life, we calculated the pooled standardised mean difference (SMD) and 95% CI for the difference in change in quality of life from baseline to follow-up between those who had quit smoking and those who had continued to smoke. For all meta-analyses we used a generic inverse variance random-effects model and quantified statistical heterogeneity using the I²statistic. We assessed the certainty of evidence for our primary outcomes using the eight GRADE considerations relevant to non-randomised studies.

MAIN RESULTS

We included 68 studies, consisting of 80,702 participants. For both primary outcomes, smoking cessation was associated with a decreased risk compared with continuous smoking: CVD death (HR 0.61, 95% CI 0.49 to 0.75; I² = 62%; 18 studies, 17,982 participants; moderate-certainty evidence) and MACE (HR 0.57, 95% CI 0.45 to 0.71; I² = 84%; 15 studies, 20,290 participants; low-certainty evidence). These findings were robust to our planned sensitivity analyses. Through subgroup analysis, for example comparing adjusted versus non-adjusted estimates, we found no evidence of differences in the effect size. While there was substantial heterogeneity, this was primarily in magnitude rather than the direction of the effect estimates. Overall, we judged 11 (16%) studies to be at moderate risk of bias and 18 (26%) at serious risk, primarily due to possible confounding. There was also some evidence of funnel plot asymmetry for MACE outcomes. For these reasons, we rated our certainty in the estimates for CVD death as moderate and MACE as low.  For our secondary outcomes, smoking cessation was associated with a decreased risk in all-cause mortality (HR 0.60, 95% CI 0.55 to 0.66; I² = 58%; 48 studies, 59,354 participants), non-fatal myocardial infarction (HR 0.64, 95% CI 0.58 to 0.72; I² = 2%; 24 studies, 23,264 participants) and non-fatal stroke (HR 0.70, 95% CI 0.53 to 0.90; I² = 0%; 9 studies, 11,352 participants). As only one study reported new onset of angina, we did not conduct meta-analysis, but this study reported a lower risk in people who stopped smoking. Quitting smoking was not associated with a worsening of quality of life and suggested improvement in quality of life, with the lower bound of the CI also consistent with no difference (SMD 0.12, 95% CI 0.01 to 0.24; I² = 48%; 8 studies, 3182 participants).  AUTHORS' CONCLUSIONS: There is moderate-certainty evidence that smoking cessation is associated with a reduction of approximately one-third in the risk of recurrent cardiovascular disease in people who stop smoking at diagnosis. This association may be causal, based on the link between smoking cessation and restoration of endothelial and platelet function, where dysfunction of both can result in increased likelihood of CVD events.  Our results provide evidence that there is a decreased risk of secondary CVD events in those who quit smoking compared with those who continue, and that there is a suggested improvement in quality of life as a result of quitting smoking. Additional studies that account for confounding, such as use of secondary CVD prevention medication, would strengthen the evidence in this area.

Management of patients after their first myocardial infarction

In the past 20 years there has been a steady improvement in the short term prognosis of patients with myocardial infarction, following the introduction of beta blockers, thrombolysis, and aspirin. Patients treated with thrombolytic drugs have a lower overall mortality after myocardial infarction but remain at risk of non-fatal reinfarction or death, and in one study almost half of all survivors of acute myocardial infarction died or suffered a further ischaemic event within three years. It is therefore important to have a strategy to identify patients at high risk, to reduce the subsequent development of cardiac failure and mortality, and to have effective measures for secondary prevention to reduce the incidence of reinfarction as well as to promote rehabilitation.

What determines mortality risk in male former cigarette smokers?

OBJECTIVES

The purpose of this study was to examine what factors determine the mortality experience of male ex-cigarette smokers, those who no longer smoke at all and those who changed to pipe or cigar smoking.

METHODS

A cohort study was undertaken with 18-year mortality data on 19,018 men.

RESULTS

Ex-cigarette smokers had an intermediate mortality risk compared with never and current smokers. Ex-cigarette smokers who switched to pipe smoking had higher mortality than those who no longer smoked at all. The mortality rates for pipe and cigar smokers who were former cigarette smokers were higher than those for pipe or cigar smokers who had never smoked cigarettes. Ex-cigarette smokers who consumed more than 20 cigarettes per day for more than 20 years experienced increased mortality for both coronary heart disease and neoplasms, even after 30 years of cessation.

CONCLUSIONS

These results support the notion that an elevated mortality risk may be seen for ex-cigarette smokers, even after they have given up smoking for many years. Ex-cigarette smokers who change to a pipe have a greater mortality risk than those who no longer smoke at all.

Risk factors, interventions and therapeutic agents in the prevention of atherosclerosis-related ischaemic diseases

Of the major risk factors for atherosclerosis, high factor VII and fibrinogen levels, genetic predisposition, gender and age cannot be influenced. Reduction of high blood pressure reduces the cerebral but not the coronary vascular risk and correction of dyslipidaemia correlates with cardiovascular risk. Other major risk factors (tobacco consumption, obesity, sedentary lifestyle and diabetes) can also be modified. Aspirin in doses of approximately 300 mg/day may be recommended for the primary prevention of myocardial infarction (MI), but only in those patients with a moderate to high risk of cardiovascular disease. Aspirin reduces the risk of fatal and nonfatal MI by about 50% and also decreases the overall mortality rate among patients with unstable angina. A lower dose of aspirin (150 mg/day) also reduces mortality by 23% in the acute phase of MI. In doses of 300 mg/day, aspirin is useful in the secondary prevention of MI and reduces the overall mortality rate by 15%. Various antiplatelet agents, including aspirin (alone or combined with dipyridamole) and ticlopidine, have proved useful in the prevention of thrombosis in aorto-coronary grafts, provided treatment begins at the latest 6 hours after surgery. The usefulness of antiplatelet drugs has been well established in the prevention of immediate reocclusion following coronary angioplasty, but not in the prevention of late reocclusion. Aspirin and ticlopidine are also beneficial in extracorporeal circulation techniques. In patients with a synthetic cardiac valve prosthesis, antivitamin K-anticoagulants are still indispensable lifelong, but their antithrombotic effect can be reinforced by dipyridamole or aspirin. Diuretics probably provide the best primary protection against cerebrovascular accidents, although medium doses of aspirin may be considered in elderly people at high risk of such accidents. Aspirin (alone or combined with dipyridamole) and ticlopidine may be recommended for the secondary prevention of cerebral ischaemic accidents. Aspirin (with or without dipyridamole) and ticlopidine reinforce the treatment of obliterative arterial disease in the lower limbs.

Course of angina pectoris after an acute coronary event

The course of postcoronary angina pectoris was examined in 555 men who had survived a first attack of myocardial infarction or unstable angina. Patients were aged less than 60 and were followed up yearly for up to 17 years. Only 25 (4.5%) had coronary artery bypass surgery. Most patients with angina were treated by nitrates alone. One year after infarction 24.1% of survivors (124/515) reported the presence of angina pectoris, and the proportions at five, 10, and 15 years were 29.9%, 30.4%, and 43.5% respectively. Seventeen years after the initial event 35.3% of the survivors had never reported postcoronary anginal symptoms. The patients who experienced anginal symptoms in the year after their coronary attack had a poorer long term survival than the group who were symptom free over the first year. These patients also had longer subsequent periods with angina, though in 41.7% angina resolved before death after a median of 2.9 years. Throughout follow up mortality during periods in which patients experienced angina was higher than in the symptom free periods. This long term follow up study of patients after a coronary event confirms that the presence or absence of angina may vary considerably over time in patients treated medically and that the presence of angina is associated with a poorer prognosis. These findings have important implications when assessing the effects of various treatment modalities on postcoronary angina, including coronary artery bypass surgery.