Archive for January, 2018

VO2 Max Equations

This post is based on this paper.

The following was created in Wolfram Language:
VO2Max Form

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Cardiopulmonary Resuscitation

Harris and Kudenchuk present an excellent review of cardiopulmonary resuscitation with practical clinical implications (Harris AW,
Kudenchuk PJ. Heart doi:10.1136/heartjnl-2017-312696).



  • Chest compression rate (AHA recommendation: 100–120/min)
  • Chest compression depth (AHA recommendation: 5–6 cm)
  • Chest compression fraction and minimising pauses (AHA
    recommendation: chest compression fraction ≥60%, minimise
    pauses in chest compressions)
  • Chest recoil (AHA recommendation: allow full chest recoil)
  • Controlled ventilation, avoiding hyperventilation (30:2 chest
    compression:ventilation ratio prior to advanced airway; 10
    breaths/min with advanced airway)



Plaque Erosion

Partida et al present an interesting paper on plaque erosion (European Heart Journal (2018) 0, 1–7, doi:10.1093/eurheartj/ehx786).


MRI in Patients with Cardiac Devices

Nazarian et al report on the safety of MRI in patients with cardiac devices.



Patients who have pacemakers or defibrillators are often denied the opportunity toundergo magnetic resonance imaging (MRI) because of safety concerns, unless the devices meet certain criteria specified by the Food and Drug Administration (termed “MRI-conditional” devices).


We performed a prospective, nonrandomized study to assess the safety of MRI at a
magnetic field strength of 1.5 Tesla in 1509 patients who had a pacemaker (58%) or an implantable cardioverter–defibrillator (42%) that was not considered to be MRI-conditional (termed a “legacy” device). Overall, the patients underwent 2103 thoracic and nonthoracic MRI examinations that were deemed to be clinically necessary. The pacing mode was changed to asynchronous mode for pacing-dependent patients and to demand mode for other patients. Tachyarrhythmia functions were disabled. Outcome assessments included adverse events and changes in the variables that indicate lead and generator function and interaction with surrounding tissue (device parameters).


No long-term clinically significant adverse events were reported. In nine MRI examinations (0.4%; 95% confidence interval, 0.2 to 0.7), the patient’s device reset to a backup mode. The reset was transient in eight of the nine examinations. In one case, a pacemaker with less than 1 month left of battery life reset to ventricular inhibited pacing and could not be reprogrammed; the device was subsequently replaced. The most common notable change in device parameters (>50% change from baseline) immediately after MRI was a decrease in P-wave amplitude, which occurred in 1% of the patients. At long-term follow-up (results of which were available for 63% of the patients), the most common notable changes from baseline were decreases in P-wave amplitude (in
4% of the patients), increases in atrial capture threshold (4%), increases in right ventricular capture threshold (4%), and increases in left ventricular capture threshold (3%). The observed changes in lead parameters were not clinically significant and did not require device revision or reprogramming.


We evaluated the safety of MRI, performed with the use of a prespecified safety protocol, in 1509 patients who had a legacy pacemaker or a legacy implantable cardioverter–defibrillator system. No long-term clinically significant adverse events were reported.


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