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High Impact Studies in Medicine

CONSENSUS 1987

Findings

Use of enalapril (ACEi) reduced mortality and improved symptoms in patients with severe congestive heart failure.

Background

Study Appraisal

Internal validity

CriteriaAcceptable?Comments
Focused
Randomized
Blinded
Similar baseline
Equal treatment
Loss to follow-up
ITT analysis
External validity
CriteriaNotes
Conflict of interests
Applicable population
Benefit vs. costs
Clinically important outcomes

ISIS II 1988

Findings

Background

Study Appraisal

Internal validity

CriteriaAcceptable?Comments
Focused
Randomized
Blinded
Similar baseline
Equal treatment
Loss to follow-up
ITT analysis
External validity
CriteriaNotes
Conflict of interests
Applicable population
Benefit vs. costs
Clinically important outcomes

4 “S” Study 1994

Scandinavian Simvastatin Survival Study

Findings

Use of simvastatin reduced death compared to placebo in patients with CHD:

  • All-cause: RR 0.7
  • Coronary deaths: RR 0.58

37% reduction of risk of myocardial revascularisation need.

Background

Study Appraisal

Internal validity

CriteriaAcceptable?Comments
Focused
Randomized
Blinded
Similar baseline
Equal treatment
Loss to follow-up
ITT analysis
External validity
CriteriaNotes
Conflict of interests
Applicable populationPatients with angina pectoris or previous MI and serum cholesterol 5.5-8.0 mmol/L on lipid-lowering diet
Benefit vs. costs
Clinically important outcomes

NINDS Trial 1995

Findings

Use of IV t-PA within 3 hours of onset of ischemic stroke improved clinical outcome at three months.

This is despite findings of increased incidence of symptomatic intracerebral hemorrhage.

No benefit (complete resolution of neurologic deficit or improvement from baseline by NIHSS score of ≥4) was observed at 24 hours compared to placebo.

Background

Prior to study, tPA used with significant caution due to IC hemorrhage. Prior studies using lower doses in very early treatment showed neurologic improvement prompting further investigation.

Study Appraisal

Internal validity

CriteriaAcceptable?Comments
FocusedY
RandomizedYStratified by time from onset of stroke
BlindedYOutcomes determined by examiners not present at treatment, CT reviewed by radiologist without clinical information for compliance.
Similar baselineYExcept for weight (in 24h post-tx) and age & aspirin use for 3 month analysis.
Equal treatmentYPlacebo protocol explicitly stated but implied to follow same bolus and infusion procedure.
Loss to follow-upY90%+ compliance to protocol. Deceased participants were given worst possible scores in data analysis.
ITT analysisYAll analysis based on ITT
External validity
CriteriaNotes
Conflict of interests
Applicable populationInclusion:
-Ischemic stroke with measurable NIHSS scale deficit
-No evidence of IC hemorrhage on CT
Exclusion:
-PMHx stroke/serious head trauma in past 3 months
-PMHx IC hemorrhage
-PMHx GI hemorrhage, urinary tract hemorrhage in past 21 days
-PMHx of arterial puncture at noncompressible site in past 7 days
-Major surgery past 14 days
-SBP >185 or DBP >110
-Suspicion of SAH
-Seizure at onset of stroke
-Taking anticoagulants or had heparin within 48h preceding stroke and had elevated PTT
-PTT >15s, platelets <100,000, or glucose <2.7 or >22.2
-If aggressive antihypertensive therapy needed
Benefit vs. costsFavourable outcomes across NIHSS, modified Rankin, and Glasgow outcome scale indicating minimal or no disability.

Risk of symptomatic intracranial bleed which resulted in deaths. Occurred more in t-Pa treated patients with more severe deficits at baseline.
Clinically important outcomest-Pa treatment used within 3 hours of ischemic stroke onset improved clinical outcomes at 3 months.

RALES 1999

Findings

Use of spironolactone (aldosterone-receptor antagonist) in conjunction with ACEi in CHF patients compared to placebo had:

  • Cardiac cause death RR 0.69
  • All cause death RR 0.70

The reduction is risk of death consistent across analyses based on serum K, NYHA class, use of K supplements, use of beta-blockers, and geographic regions.

More patients saw reduction in NYHA class and fewer patients saw worsening in the spironolactone group compared to placebo

The trial was ended early as the benefits of spironolactone exceeded prespecified values.

Background

Aldosterone is important in the pathophysiology of heart failure. Prior to this study, treatment of CHF with LVEF consisted of ACEi, loop diuretic, and digoxin.
tor blocker is also relatively contraindicated due to risk of hyperkalemia.

Study Appraisal

Internal validity

CriteriaAcceptable?Comments
FocusedY
RandomizedY
BlindedYDouble blinded to matched placebo
Similar baselineY
Equal treatmentY?Protocol in place for side effects of tx arm but appears to have been applied to control too
Loss to follow-upYPts who stopped treatment were still included in analysis
ITT analysisY
External validity
CriteriaNotes
Conflict of interests
Applicable populationInclusion:
-NYHA class IV within 6 months prior to enrolment and class III or IV at environment
-Diagnosed at least 6 weeks prior
-Treated with ACEi (if tolerated) and loop diuretic (digitalis and vasodilator also ok, potassium-sparing diuretics not ok)
-LVEF ≤35%
Exclusion:
-PMHx of Primary operable valvular heart disease, congenital HD, unstable angina, primary hepatic failure, active cancer, any life-threatening disease
-Hx heart transplant or waiting procedure
-Serum creatinine >221 mcmol/L
-Serum K >5 mmol/L
Benefit vs. costsSlight risk of hyperkalemia but very insignificant relative to benefit
Clinically important outcomesReduction in death, reduced cardiac remodelling when used with ACEi

HOPE 2000

Heart Outcome Prevention Evaluation

Findings

In patients with vascular disease or diabetes and with cardiovascular risk factor(s), ramipril reduced:

  • Death from cardiovascular causes (RR 0.74)
  • MI (RR 0.80)
  • Stroke (RR 0.68)
  • All cause death (RR 0.84)
  • Revascularization procedures (RR 0.85)
  • Cardiac arrest (RR 0.63)
  • Heart failure (RR 0.77)
  • Diabetic complications (RR 0.84)

NNT = ~15

Background

RAAS is implicated in risk of cardiovascular events. Prior research had shown ACEi is beneficial in patients with low ejection fraction. This study addresses use of ACEi in patients beyond those with low ejection fraction.

Study Appraisal

Internal validity

CriteriaAcceptable?Comments
FocusedY
RandomizedY
BlindedYDouble-blinded (10mg v. 2.5mg v. placebo)
Similar baselineY
Equal treatmentY
Loss to follow-upY
ITT analysisY~30% discontinued in both arms but included in analysis
External validity
CriteriaNotes
Conflict of interests
Applicable populationInclusion:
-≥55 years old
-Hx of CAD, stroke, peripheral vascular disease, or diabetes + one other cardiovascular RF
Exclusion:
-Hx of HF, or low ejection fraction (<40%)
-Taking ACEi or vitamin E
-Uncontrolled hypertension or overt nephropathy
-PMHx MI or stroke within 4 weeks prior to study
Benefit vs. costs
Clinically important outcomesUse of ACEi reduced CV events.

MERIT – HF 2000

Metoprolol controlled/Extended-release Randomized Intervention Trial in congestive Heart Failure

Findings

In patients with chronic HF with NYHA class II-IV and ejection fraction ≤40% incidence of the following were lower in the metoprolol CR/XL group than placebo:

  • All-cause mortality/hospitalization (RR 0.81)
  • All-cause mortality/hospitalization due to worsening heart failure (RR 0.69)
  • Death or heart transplantation (RR 0.68)
  • Cardiac death or nonfatal acute MI (RR 0.61)

The study was terminated at halfway point as predefined criterion was met and exceeded.

Background

Study Appraisal

Internal validity

CriteriaAcceptable?Comments
FocusedY
RandomizedY
BlindedYSingle-blinded placebo run in period, double-blind placebo controlled trial
Similar baselineY
Equal treatmentY
Loss to follow-upY
ITT analysisY
External validity
CriteriaNotes
Conflict of interests
Applicable populationInclusion:
-Symptomatic HF for ≥3 months
-NYHA class II-IV and LVEF ≤40%
-LVEF 36-40%: symptomatic minimum cutoff
-Age 40-80
Exclusion:
-Acute MI or unstable angina within 28 days before randomization
-Indication or contraindication for treatment with beta-1 blockade
-Severe decompensated HF (eg. pulmonary edema)
-Supine SBP <100 mmHg
Benefit vs. costs
Clinically important outcomesUse of metoprolol CR/XL once daily in addition to conventional HF treatment reduced worsening HF and need for hospitalization.

Heart Protection Trial 2002

Findings

In patients with coronary disease, other occlusive arterial disease, or diabetes, use of simvastatin compared to placebo reduced:

  • All-cause mortality (RR 0.877)
  • Death from vascular causes (RR 0.835)
  • Death from coronary causes (RR 0.82)

Background

Prior trials (incl. the 1994 4S Study) showed use of statins reduced coronary mortality and morbidity in certain high-risk patients. Little evidence was available for patients on other high-risk groups such as patients with diabetes but without diagnosed coronary disease, females, elderly, and those with lower LDL-C concentrations.

Study Appraisal

Internal validity

CriteriaAcceptable?Comments
FocusedY
RandomizedY
BlindedY
Similar baselineY
Equal treatmentY
Loss to follow-upY
ITT analysisYAccounts for non-study statins prescribed due to increased LDL which were either addition to study dose or placebo
External validity
CriteriaNotes
Conflict of interests
Applicable populationMen and women aged 40-80 years old with non-fasting total cholesterol of ≥3.5 mmol/L and at substantial 5-year risk of death from CAD due to PMHx.
Benefit vs. costs
Clinically important outcomesStatins reduced all-cause mortality for secondary prevention following cardiovascular event

AFFIRM 2002

Atrial Fibrillation Follow-up Investigation of Rhythm Management

Findings

In patients with atrial fibrillation, rhythm control offered no survival advantage compared to rate control (HR 1.15 (CI: 0.99-1.34, P=0.08)).

The rhythm group had more hospitalization and more adverse drug effects.

Background

Current treatment paradigms allows for two approaches to treatment of atrial fibrillation:

  • Cardioversion followed by antiarrhythmics to maintain sinus rhythm
  • Use of rate-controlling medications and allowing afib to persist

In both case, anticoagulants are indicated.

Study Appraisal

Internal validity

CriteriaAcceptable?Comments
FocusedY
RandomizedY
BlindedNTreatment option choices was decided by treating physician, thus clinicians aware of which arm. Additionally, rhythm and rate control are symptomatically different.
Similar baselineY
Equal treatmentN?Rhythm control arm required cardioversion
Loss to follow-upY
ITT analysisYCross-over rate from each arm analyzed and deemed acceptable
External validity
CriteriaNotes
Conflict of interests
Applicable populationPatients ≥65 years old or had other risk for stroke or death. Atrial fibrillation must have been assessed to likely be recurrent, likely to cause illness or death, and long term treatment was warranted.
Benefit vs. costs
Clinically important outcomesUse of rate-control was not inferior to rhythm control. When accounting for adverse effects, may be superior.

ACTIVE W 2006

Atrial fibrillation Clopidogrel Trial with Irbesartan for prevention of Vascular Events

  • ACTIVE A = Clopidogrel + aspirin vs. placebo + aspirin
  • ACTIVE W = Clopidogrel + aspirin vs. oral anticoagulation
  • ACTIVE I = Irebesartan with ACTIVE A or W participants

Findings

In patients with atrial fibrillation, clopidogrel and aspirin compared to oral anticoagulation therapy saw higher risk of:

  • Stroke (RR 1.72)
  • Non-CNS systemic embolism (RR 4.66)
  • Minor bleeds

Comparison saw similar rates of:

  • Total mortality (RR 1.01, CI 0.81-1.26; p=0.91)
  • Major hemorrhage

Background

Atrial fibrillation increases the risk of stroke and other vascular events. Oral anticoagulation typically consisted of warfarin which was shown to reduce risk of stroke and CV events significantly. However, risk of major bleeding increased by 70% compared to just aspirin.

Additionally, warfarin required regular INR monitoring.

Study Appraisal

Internal validity

CriteriaAcceptable?Comments
FocusedY
RandomizedY
BlindedNOpen treatment but blinded adjudication of outcomes
Similar baselineY
Equal treatmentNOpen treatment + INR measurement
Loss to follow-upY
ITT analysisY
External validity
CriteriaNotes
Conflict of interests
Applicable populationInclusion
-ECG evidence of afib
-At least one of the following:
Age 75 or older
On treatment for htn
Previous stroke, TIA, or non-CNS systemic embolus
LVEF <45%
PAD
Age 55-74 if diabetes or CAD
Exclusion
-CI for medications
-Peptic ulcer disease in previous 6 months
-PMHx IC hemorrhage
-Significant thrombocytopenia
-Mitro stenosis
Benefit vs. costs
Clinically important outcomesOral anticoagulation therapy is superior to clopidogrel + aspirin for afib pervention of stroke

HYVET 2008

Findings

In patients who are 80 years of age or older (mean BP 173/91), treatment with antihypertensive therapy (mean BP 15/6 lower than placebo) compared to placebo reduced:

  • Rate of fatal or nonfatal stroke (RR 0.70)
  • Rate of death from stroke (RR 0.61)
  • Rate of all-cause death (RR 0.79)
  • Rate of death from cardiovascular causes (RR 0.77)
  • Rate of heart failure (RR 0.36)

Background

It is well-established that antihypertensive therapy is beneficial in many subpopulations. However, the benefits of treating older patients is inconclusive.

Prior studies have shown elevated BP is associated with:

  • Risk of stroke
  • Risk of death

However, epidemiologic studies have shown BP and risk of death are inversely related among people aged 80 or older, possibly suggesting risk of antihypertensive therapy or conditions associated with BP reduction (cancer, dementia, MI, HF).

Study Appraisal

Internal validity

CriteriaAcceptable?Comments
FocusedYEnd points: stroke (not incl. TIA), death from various causes/all causes
RandomizedY
BlindedYDouble
Similar baselineY
Equal treatmentYIncluding “adjustment” dose placebo
Loss to follow-upY
ITT analysisY
External validity
CriteriaNotes
Conflict of interests
Applicable populationInclusion
-Aged ≥80
-Persistent htn (SBP>160)
Exclusion
-CI to meds
-Accelerated or secondary htn
-Hemorrhagic stroke in previous 6 months
-HF requiring antihypertensive treatment
-Serum creatinine >160 mcmol/L
-Serum K <3.5 or >5.5 mmol/L
-Gout
-Diagnosis of clinical dementia
-Required nursing care
Benefit vs. costs
Clinically important outcomesTreatment with sustained release indapamide ± perindopril beneficial in terms of adverse outcomes

PLATO 2009

PLATelet inhibition and patient Outcomes

Findings

In patients with ACS, use of ticagrelor with aspirin compared to clopidogrel with aspirin reduced the occurrence of:

  • Death from vascular causes, MI, or stroke (HR 0.84)
  • Death from composite of cardiac/vascular causes (HR 0.88)

The groups did not differ significantly in terms of rates of major bleeding.

Background

Prior clinical practical guidelines recommend dual antiplatelet treatment for patients with ACS. This consist of aspirin and clopidogrel.

Clopidogrel requires a slow and variable prodrug to active metabolite mechanism which results in nonideal platelet inhibition.

Tricagrelor is an reversible and direct-acting antagonist of P2Y12 which provides better inhibition than clopidogrel.

Study Appraisal

Internal validity

CriteriaAcceptable?Comments
FocusedY
RandomizedY
BlindedY
Similar baselineY
Equal treatmentY
Loss to follow-upY
ITT analysisY
External validity
CriteriaNotes
Conflict of interests
Applicable population-Hospitalized for ACS w/ ST-segment elevation
-Hospitalized for ACS w/o ST elevation but with other indicators of acute heart disease (eg. troponin, ST changes, PMHx)
-Onset of symptom within 24 hrs
Benefit vs. costs
Clinically important outcomesSuperior performance of primary end points of ticagrelor vs clopidogrel with similar rates of major bleed.

ACTIVE A 2009

Atrial fibrillation Clopidogrel Trial with Irbesartan for prevention of Vascular Events

  • ACTIVE A = Clopidogrel + aspirin vs. placebo + aspirin
  • ACTIVE W = Clopidogrel + aspirin vs. oral anticoagulation
  • ACTIVE I = Irebesartan with ACTIVE A or W participants

Findings

In patients with atrial fibrillation unsuitable for vitamin K-antagonist therapy, use of clopidogrel + aspirin compared to just aspirin reduced:

  • Risk of stroke (RR 0.72)
  • Risk of vascular events (0.89)

Use of clopidogrel increased risk of major bleed (RR 1.57).

Background

Atrial fibrillation increases the risk of stroke and other vascular events. Oral anticoagulation typically consisted of warfarin which was shown to reduce risk of stroke and CV events significantly.

Study Appraisal

Internal validity

CriteriaAcceptable?Comments
FocusedY
RandomizedY
BlindedY
Similar baselineY
Equal treatmentY
Loss to follow-upY
ITT analysisY
External validity
CriteriaNotes
Conflict of interests
Applicable population-Diagnosed afib
-Risk factor(s) for stroke
-Unable to use vitamin K antagonist
Benefit vs. costs
Clinically important outcomes

ROCKET AF 2011

Rivaroxaban Once-daily oral direct factor xa inhibition Compared with vitamin K antagonism for prevention of stroke and Embolism Trial in Atrial Fibrillation

(Rivaroxaban Once-daily Compared with vitamin K antagonism for prevention of stroke and Embolism Trial)

Findings

In patients with nonvalvular atrial fibrillation and increased risk of stroke, use of rivaroxaban compared to dose-adjusted warfarin reduced:

  • Occurrence of stroke or systemic embolism (HR 0.79, ITT HR 0.88)

Similar rates of major and nonmajor clinically relevant bleeding (HR 1.03, CI 0.96-1.11).

Background

Atrial fibrillation associated with risk of stroke. Vitamin K antagonists (warfarin) are effective at stroke prevention but require frequent INR monitoring and dose adjustments.

Rivaroxaban is a direct factor Xa inhibitor that is more consistent at anticoagulation than warfarin.

Study Appraisal

Internal validity

CriteriaAcceptable?Comments
FocusedY
RandomizedY
BlindedY
Similar baselineY
Equal treatmentYYes including fake INR values for rivaroxaban arm
Loss to follow-upY
ITT analysisY
External validity
CriteriaNotes
Conflict of interests
Applicable populationInclusion:
-Non-valvular atrial fibrillation
-Moderate to high risk for stroke
Benefit vs. costs
Clinically important outcomes

ARISTOTLE 2011

Apixaban for Reduction In STroke and Other ThromboemboLic Events in atrial fibrillation.

Findings

In patients with nonvalvular atrial fibrillation and increased risk of stroke, use of rivaroxaban compared to dose-adjusted warfarin reduced:

  • Occurrence of stroke or systemic embolism (HR 0.79, p<0.001 for noninferiority, p=0.01 for superiority)
  • Rate of major bleed (HR 0.66)
  • Rate of death (HR 0.89)

Background

Atrial fibrillation associated with risk of stroke. Vitamin K antagonists (warfarin) are effective at stroke prevention but require frequent INR monitoring and dose adjustments.

Apixaban is a direct factor Xa inhibitor that is more consistent at anticoagulation than warfarin.

Study Appraisal

Internal validity

CriteriaAcceptable?Comments
FocusedY
RandomizedY
BlindedY
Similar baselineY
Equal treatmentY?Unclear if INR for apixaban group was checked
Loss to follow-upY
ITT analysisY
External validity
CriteriaNotes
Conflict of interests
Applicable populationInclusion:
-Afib or aflutter with 2 episodes prior
-Risk factor for stroke
Exclusion:
-Afib was due to reversible cause
-Mod/severe mitral stenosis
-Other conditions requiring anticoag
-Need for antiplatelet or severe renal impairment
Benefit vs. costs
Clinically important outcomesApixaban is superior to warfarin for prevention of stroke or systemic embolism, caused less bleeding, and resulted in lower mortality

PARADIGM 2014

Prospective comparison of ARni with Acei to Determine Impact on Global Mortality and morbidity in heart failure trial

Findings

In adult patients with reduced ejection fraction heart failure, use of sacubitril/valsartan (Entresto), an angiotensin receptor-neprilysin inhibitor, compared to an ACEi reduced:

  • All cause mortality (HR 0.84)
  • Cardiovascular causes mortality (HR 0.80)
  • Risk of hospitalization for HF by 21%

Study ended prematurely due to overwhelming benefit.

Background

Established treatment for CHF have included ACE inhibitors for decades (see CONSENSUS 1987). Angiotensin-receptor blockers have been thought to be equivalent, although the evidence is less consistent, and has thus been used in patients who have ACEi-associated side effects.

Neprilysin degrades endogenous vasoactive peptides (natriuretic peptides, bradykinin, adrenomedullin) which causes vasoconstriction, sodium retention, and maladaptive remodelling. Inhibition of neprilysin would counter this.

Entresto is a combination of an ARB and neprilysin inhibitor.

Study Appraisal

CriteriaAcceptable?Additional Comments
Internal validityYes
External validityYes

SPRINT 2015

Systolic blood PRessure INtervention Trial

Findings

Along patients with high risk of cardiovascular events (but without diabetes/prior stroke), a systolic blood pressure target of <120 mmHg compared to a target of <140 mmHg reduced:

  • Cardiovascular events (ACS, stroke, HF, death from CVD) (HR 0.75)
  • All-case mortality (HR 0.73)

Risk of adverse events were higher in the lower target group:

  • Hypotension (HR 1.67)
  • Syncope (HR 1.33)
  • Electrolyte abnormalities (HR 1.35)
  • Acute kidney injury (HR 1.66)

Limitations
Study population limited to those with:

  • Age ≥50
  • Increased risk of cardiovascular events (CKD, >15% on Framingham score, age ≥75)

The study also excluded patients with either:

  • Diabetes
  • Prior stroke

Background

Treatment of hypertension reduces risk of cardiovascular outcomes. However, the target SBP was uncertain with studies suggesting risk begins with SBP above 115 to 150 mmHg.

Study Appraisal

CriteriaAcceptable?Additional Comments
Internal validityY
External validityY

EMPA-REG-OUTCOME 2015

EMPAgliflozin Removal of Excess Glucose: cardiovascular OUTCOME event trial in type 2 diabetes mellitus patients

Findings

In adult patients with type 2 diabetes at high risk of cardiovascular events, use of empagliflozin, an SGLT2 inhibitor, compared to placebo, saw reduced:

  • Death from cardiovascular causes, nonfatal MI, or nonfatal stroke (composite; HR 0.86)
  • Death from cardiovascular causes (RR 0.62)
  • Hospitalization from heart failure (RR 0.65)
  • All cause mortality (RR 0.68)

The intervention group saw higher rates of genital infection but no imbalance for uncomplicated or complicated UTI.

Background

While type 2 diabetes and cardiovascular disease both increase the risk of death, evidence for the benefit of glucose lowering therapy on reducing cardiovascular events and death has been unclear.

In particular, prior antihyperglycemics have caused adverse cardiovascular events (rosiglitazone) and thus addition vigilance was required.

Sodium-glucose cotransporter 2 (SGLT2) inhibitors reduce blood glucose levels by increasing urinary glucose excretion. Other effects included:

  • Weight loss
  • Reduction in blood pressure without increases in heart rate
  • Favourable effect on markers of arterial stiffness and vascular resistance

Study Appraisal

CriteriaAcceptable?Additional Comments
Internal validityY
External validityY

TAVR Low-Risk Trials 2019

Findings

Limitations

Background

Study Appraisal

CriteriaAcceptable?Additional Comments
Internal validity
External validity

RECOVERY 2020

Findings

Limitations

Background

Study Appraisal

CriteriaAcceptable?Additional Comments
Internal validity
External validity

EMPEROR PRESERVED 2021

Findings

Limitations

Background

Study Appraisal

CriteriaAcceptable?Additional Comments
Internal validity
External validity

STEP1 2021

Findings

Limitations

Background

Study Appraisal

CriteriaAcceptable?Additional Comments
Internal validity
External validity

SELECT 2023

Findings

Limitations

Background

Study Appraisal

CriteriaAcceptable?Additional Comments
Internal validity
External validity

BALANCE 2024

Findings

Limitations

Background

Study Appraisal

CriteriaAcceptable?Additional Comments
Internal validity
External validity

CRASH 2013

Findings

Limitations

Background

Study Appraisal

CriteriaAcceptable?Additional Comments
Internal validity
External validity

COBRRA 2026

Findings

Limitations

Background

Study Appraisal

CriteriaAcceptable?Additional Comments
Internal validity
External validity