From the Guidelines
The patient's increased resting heart rate of 90 bpm with sinus rhythm post-mitral valve surgery is likely a compensatory response to asymptomatic hypotension, and close monitoring rather than immediate intervention is appropriate, as indicated by the 2009 ACCF/AHA focused update on perioperative beta blockade 1. The increased resting heart rate in this patient could be attributed to several factors, including:
- The inflammatory response to surgical trauma
- Pain
- Medication effects, such as withdrawal of pre-operative beta-blockers or initiation of inotropes
- Fluid shifts
- Mild anemia from surgical blood loss
- A compensatory response to the hypotension, as the body attempts to maintain cardiac output, especially if there is relative hypovolemia or decreased stroke volume, as discussed in the context of postoperative arrhythmias and conduction disorders 1. The sinus rhythm is reassuring, indicating the conduction system is functioning properly despite the stress of surgery. Since the patient is asymptomatic despite the hypotension, close monitoring rather than immediate intervention may be appropriate, with a focus on:
- Ensuring adequate pain control
- Optimizing fluid status
- Gradually reintroducing pre-operative cardiac medications as tolerated to help normalize the heart rate. However, if the tachycardia persists beyond the expected post-operative period (3-5 days), further evaluation for infection, pulmonary embolism, or myocardial ischemia would be warranted, considering the potential for postoperative arrhythmias and conduction disorders 1.
From the Research
Possible Causes of Increased Resting Heart Rate Post-Mitral Valve Surgery
- The patient's increased resting heart rate to 90 beats per minute (bpm) and sinus rhythm post-mitral valve surgery could be due to various factors, including the body's response to the surgical procedure and the subsequent changes in cardiac function 2.
- Atrial fibrillation, a common disturbance of heart rate in patients with mitral valvular disease, may have been normalized after the mitral valve replacement, resulting in an increased heart rate 2.
- The presence of chronic atrial fibrillation before the operation may have been converted to sinus rhythm after the surgery, leading to an increased heart rate 2.
- Postoperative atrial tachycardias, including atrial fibrillation, are common arrhythmias occurring late after mitral valve surgery, and may contribute to an increased resting heart rate 3.
- The underlying mechanism of the increased heart rate could be macroreentry, which is the predominant atrial tachycardia mechanism in patients with prior mitral valve surgery 3.
Relationship Between Mitral Valve Surgery and Heart Rate
- Mitral valve surgery can affect the heart's electrical conduction system, leading to changes in heart rate and rhythm 4.
- The imposition of dyssynchrony with right ventricular pacing may further compromise stroke volume and contribute to an increased heart rate 4.
- The long-term risk of heart failure and mortality following mitral valve surgery is not significantly altered by the presence of a right ventricular pacemaker 4.
Asymptomatic Hypotension
- Asymptomatic hypotension, with blood pressure readings in the 90s/60s, may be related to the patient's increased heart rate and cardiac output post-mitral valve surgery 5.
- Elevated postprocedural mitral valve pressure gradient may be an independent predictor of adverse clinical and functional outcomes in patients with degenerative mitral regurgitation, but its relationship to asymptomatic hypotension is unclear 5.