Tag Archives: heart

Magnesium in asthma limits tachycardia

Dr WFS Sellers and colleagues describe several cases that demonstrate convincingly a protective effect of intravenous magnesium sulphate against the tachycardia produced by intravenous salbutamol in patients with asthma. This effect was observed both when magnesium was given before and when given after the salbutamol. It was seen in critically ill asthmatic patients and in a volunteer with well-controlled asthma.

Intravenous magnesium sulphate increases atrial contraction time and refractory times. It is used to treat atrial tachyarrhythmias and has a negative chronotropic and dromotropic effect.
Intravenous magnesium sulphate prevents intravenous salbutamol tachycardia in asthma
Br J Anaesth. 2010 Dec;105(6):869-70

CPAP in LVF again

Another stab at assessing noninvasive ventilation in cardiogenic pulmonary oedema has been made by Italian researchers who compared CPAP with noninvasive pressure support ventilation (nPSV – similar to BiPAP) in a randomised trial of  80 patients. The primary outcome was endotracheal intubation rates. There was no significant difference between the two modalities. This result is in keeping with the much larger 3CPO trial.

Continuous Positive Airway Pressure vs. Pressure Support Ventilation in Acute Cardiogenic Pulmonary Edema: A Randomized Trial
J Emerg Med. 2010 Nov;39(5):676-84

GPIIb/IIIa inhibitors

A systematic review on use of GPIIb/IIIa inhibitors in NSTEACS has been updated as part of the Annals of Emergency Medicine‘s Evidence Based Emergency Medicine series. The bottom line:
In patients with non-ST-segment elevation acute coronary syndromes who do not undergo early percutaneous coronary intervention, administration of platelet glycoprotein IIb/IIIa (GPIIb/IIIa) inhibitors, given in addition to aspirin and unfractionated heparin, does not reduce 30-day or 6-month mortality. For the composite endpoint of myocardial infarction or death, there was modest benefit at 30 days and 6 months; however, there was an increased risk of major hemorrhage among those receiving GPIIb/IIIa inhibitors.
Update: Use of Platelet Glycoprotein IIb/IIIa Inhibitors in Patients With Unstable Angina and Non-ST-Segment Elevation Myocardial Infarction
Annals of Emergency Medicine Volume 56, Issue 5 , Pages e1-e2, November 2010

Compare this with the recommendations of the European Resuscitation Council who provide the following summary regarding this class of drug:
Gp IIB/IIIA receptor inhibition is the common final link of platelet aggregation. Eptifibatide and tirofiban lead to reversible inhibition, while abciximab leads to irreversible inhibition of the Gp IIB/IIIA receptor. Older studies from the pre-stent era mostly support the use of this class of drugs. Newer studies mostly document neutral or worsened outcomes. Finally in most supporting, as well as neutral or opposing studies, bleeding occurred in more patients treated with Gp IIB/IIIA receptor blockers. There are insufficient data to support routine pre-treatment with Gp IIB/IIIA inhibitors in patients with STEMI or non-STEMI-ACS. For high-risk patients with non-STEMI-ACS, in-hospital upstream treatment with eptifibatide or tirofiban may be acceptable whereas abciximab may be given only in the context of PCI. Newer alternatives for antiplatelet treatment should be considered because of the increased bleeding risk with Gp IIB/IIIA inhibitors when used with heparins.
European Resuscitation Council Guidelines for Resuscitation 2010 Section 5. Initial management of acute coronary syndromes
Resuscitation 81 (2010) 1353–1363 – full text downloadable

McConnell's sign revisited

In acute pulmonary embolism, a well-recognised pattern of right ventricular wall motion reported by McConnell is characterised by normal RV apex (RVa) contractility with akinesia of the RV free wall. A study using an echo techique called longitudinal velocity vector imaging (VVI) was conducted to describe RVa mechanics in relation to the rest of the RV in patients with a proven acute PE (aPE) and to compare these results to healthy volunteers and to patients with known chronic pulmonary hypertension (cPH). There were no significant differences in segmental strain patterns between the aPE and cPH groups. The authors suggest that McConnell’s sign is probably a visual illusion; preserved RVa contractility might be due to tethering of the RVa to a hyperdynamic left ventricle in the presence of an acutely dilated RV and this is the most likely explanation of the regional pattern of RV dysfunction seen in aPE patients.
Video describing McConnell’s sign from YouTube:

Right Ventricular Apical Contractility in Acute Pulmonary Embolism: The McConnell Sign Revisited
Echocardiography. 2010 Jul;27(6):614-20

Fancy new ACS tests

It’s hard to keep track of all new proposed biomarkers that may be useful in the work up of acute coronary syndrome (ACS) patients. We’re all used to troponin now – so we really want to know how novel tests measure up against the existing standard, in particular for the timeframe in which troponin is less helpful, namely the first six hours.
A systematic review examine the evidence for the following biomarkers in the early assessment (ie, within 6 h of symptom onset) of suspected ACS:

  • CK-MB: CK-MB and 2 h ΔCK-MB have potential in diagnosing AMI in the first hours after symptom onset. Whether CK-MB has value in the early diagnostic assessment of ACS in addition to clinical symptoms, ECG or other markers has rarely been studied.
  • myoglobin: myoglobin might be of value in early ruling out of AMI and ACS in suspected patients because of the relatively high NPV; its PPV, however, is low. However, it is not yet known whether myoglobin has diagnostic value in addition to symptoms, signs and other diagnostic tests (eg, ECG), because of the lack of multivariable analysis
  • heart-type fatty acid binding protein (H-FABP): H-FABP seems to have some potential as an early diagnostic marker of AMI or ACS, but its value in addition to clinical features and other markers has not been studied
  • ischemia modified albumin (IMA): IMA could be a potential marker for early ruling out of ACS in chest pain patients because of its relatively high NPV, especially combined with cTn and ECG. However, its PPV is low. Importantly; IMA seems to add relevant diagnostic information to more readily available diagnostic parameters. However, problems with the stability of IMA and its lack of cardiospecificity have been reported
  • pregnancy-associated plasma protein A: contradictory results indicate that the diagnostic value of PAPP-A in patients suspected of having ACS has not been evaluated properly
  • glycogen phosphorylase isoenzyme BB: GPBB might be a marker for myocardial ischaemia and myocardial necrosis, although the available research is limited and does not assess the added value of the marker.
  • myeloid-related protein 8/14: more research is needed to evaluate the (added) diagnostic value of MRP 8/14 in patients suspected of having ACS.

The authors also point out the introduction of high-sensitivity troponin assays may further improve diagnosis of ACS. They refer to a study in patients with suspected AMI presenting at the emergency department, which showed that a sensitive cTnI assay had a higher NPV than a standard cTnT assay and comparable PPV for detecting AMI within 6 h of symptom onset. The PPV was 79.3% and 80.7%, respectively; the NPVs were 95.3% and 88%. The Full Text of this high-sensitivity troponin paper is here
The review makes the following conclusions:

  • current guidelines advocate the use of cardiac troponin or CK-MB when cTn is not available, and myoglobin in the first 6 h in addition to cTn
  • IMA and H-FABP seem to be promising diagnostic biomarkers in the early diagnostic assessment of patients suspected of having ACS
  • There is an urgent need for adequately designed studies of (novel) ACS markers and their combinations against contemporary troponin assays

Novel biochemical markers in suspected acute coronary syndrome: systematic review and critical appraisal
Heart. 2010 Jul;96(13):1001-1

Thoracic electrical bioimpedance in dyspnoea

Thoracic electrical bioimpedance (TEB) was used in ED patients presenting with dyspnoea to differentiate between cardiac and non-cardiac causes.
The fundamental principle behind TEB is based on Ohm’s law. If a constant electrical current is applied to the thorax, changes in impedance (ΔZ) to flow are equal to changes in voltage drop across the circuit. As a current will always seek the path of lowest resistivity, which in the human body is blood, ΔZ of the thorax will primarily reflect the dynamic changes of blood volume in the thoracic aorta. Changes in thoracic electrical impedance are continuously recorded and processed using a computer algorithm to calculate a number of cardiohaemodynamic parameters such as stroke volume, CO, CI, SVR and systemic vascular resistance index (SVRi).

A cardiac index cut-off of 3.2 l/m/m2 had a 86.7% sensitive (95% CI 59.5% to 98.0%) and 88.9% specific (95% CI 73.9% to 96.8%) for cardiac dyspnoea in the 52 patients studies, of which 15 had cardiac-related dyspnoea.
The study has several limitations including small numbers and using the gold standard of discharge diagnosis.
Thoracic electrical bioimpedance: a tool to determine cardiac versus non-cardiac causes of acute dyspnoea in the emergency department
Emerg Med J. 2010 May;27(5):359-63
Free Full Text

Bloodtest Not Pertinent (BNP)

Despite a lack of evidence that it’s useful, many emergency departments have introduced BNP testing. Some smart Australians decided to properly evaluate its benefit the best way possible – with a randomised controlled trial on 612 patients with acute severe dyspnoea. Guess what? Clinician knowledge of BNP values in patients who presented with shortness of breath to the emergency department did not reduce the probability of hospital admission or alter management or length of hospital stay. The study findings do not support indiscriminate BNP testing in all dyspnoea patients, but do not rule out a possible role in patients with milder dyspnoea.
B-type natriuretic peptide testing, clinical outcomes, and health services use in emergency department patients with dyspnea: a randomized trial
Ann Intern Med. 2009 Mar 17;150(6):365-71

STEMI and PCI guidelines

Lots of interesting and up to date information in this thick document from December 2009
Full text is available here
2009 Focused Updates: ACC/AHA Guidelines for the Management of Patients With ST-Elevation Myocardial Infarction (Updating the 2004 Guideline and 2007 Focused Update) and ACC/AHA/SCAI Guidelines on Percutaneous Coronary Intervention (Updating the 2005 Guideline and 2007 Focused Update)

Echo best test for acute LVF in ED

Three diagnostic tests for acute left ventricular heart failure in dyspnoeic patients were compared, with the gold standard being the diagnosis by three independent reviewers (two cardiologists and one respiratory physician) who were blinded to the results of the tests being examined. The tests in question were  NT-proBNP, the Boston criteria, and limited echo performed by emergency physicians.
The primary goal of the echo study was the detection of the following echocardiographic variables, expressed as present or absent: reduced LV ejection fraction (LV ejection fraction <50% on subjective visual estimation of the change in LV size between diastole and systole) and the ‘‘restrictive’’ pattern on pulsed Doppler analysis of mitral inflow (using the apical view).
According to the authors, pulsed Doppler analysis of mitral inflow can be described by three patterns: 1) an ‘‘impaired relaxation’’ pattern, suggesting no increase in LV filling pressures; 2) a ‘‘normal’’ or ‘‘normalized’’ pattern; and 3) a restrictive pattern, suggesting an increase in LV filling pressures.

Trained emergency physicians were able to perform EDecho in a median of 4 minutes, obtaining Doppler data in an average of 80% of patients presenting for acute dyspnea. Considering the 125 patients with both EDecho variables available, reduced LV ejection fraction was less accurate than the restrictive mitral pattern for the diagnosis of aLVHF. The restrictive pattern was more sensitive (82%) and specific (90%) than reduced LV ejection fraction and more specific than the Boston criteria and NT-proBNP for the diagnosis of aLVHF. The accuracy of the restrictive pattern in the overall population was 75%, compared with accuracy of 49% for both NT-proBNP and Boston criteria.
Diagnostic accuracy of emergency Doppler echocardiography for identification of acute left ventricular heart failure in patients with acute dyspnea: comparison with Boston criteria and N-terminal prohormone brain natriuretic peptide.
Acad Emerg Med. 2010 Jan;17(1):18-26

Myocardial infarction not so common in LBBB?

An observational cohort study of 7937 ED visits by patients presenting with chest pain or ‘ischemic equivalent’ (shortness of breath for which ACS was considered a possible cause) was done to examine the relationship between left bundle branch block (LBBB) on the ECG and the incidence of acute myocardial infarction (AMI). No difference was observed in the rates of AMI in patients with new or presumed new LBBB, old LBBB, and no LBBB. The authors suggest that this large cohort of undifferentiated ED patients may be more reflective of the true prevalence of AMI in LBBB (7.3% in this study) and question the appropriateness of a liberal fibrinolytic strategy for such patients. Another argument for primary PCI?
Lack of association between left bundle-branch block and acute myocardial infarction in symptomatic ED patients
Am J Emerg Med. 2009 Oct;27(8):916-21