Heart rate as an early predictor of severe cardiomyopathy and increased mortality in peripartum cardiomyopathy
Ryan Cooney MD1 | John R. Scott MPH2 | Madeline Mahowald MD3 | Elizabeth Langen MD4 | Garima Sharma MD5 | David P. Kao MD6 | Melinda B. Davis MD7
Take Home Points
- Early detection of peripartum cardiomyopathy (PPCM) is desirable to optimise intra/post partum care and to plan for safe delivery.
- Heart rate is a risk indicator of morbidity and mortality in patients known to have chronic heart failure.
- This retrospective analysis sought to assess the relationship between heart rate and outcomes in women with PPCM.
- 82 patients met inclusion criteria. Mean LVEF at the point of diagnosis of PPCM was 26 +/- 11.1%
- Sinus tachycardia (HR >100) was present in 61% of patients (n=50) at the time of diagnosis.
- Heart rate predicted lower LVEF (F=30.00, p<0.0001).
- In an age adjusted logistic regression model, heart rate at diagnosis was associated with a 5x higher risk of mortality when HR at diagnosis was >110 per minute (adjusted OR 5.35, CI 1.23-23.28, p=0.025).
- Sinus tachycardia in the peripartum period is associated with worse LVEf and so should be considered a ‘red flag’ for potential PPCM.
- This reaffirms that pregnant women with a tachycardia should be thoroughly assessed for usual reversible causes but if none are found, assessment of LV function should be considered.
Resting heart rate is a risk indicator of morbidity and mortality in patients with a variety of cardiovascular conditions. Put very simply, a climbing heart rate, in the absence of other reversible causes e.g. anaemia, infection, thyrotoxicosis, pain, anxiety state etc. suggests that there may be cardiac dysfunction – resting heart rate increases to maintain adequate cardiac output. Heart rate is a very simple yet sensitive indicator of something amiss.
This was a retrospective analysis of patients living in the Michigan region whom were diagnosed with PPCM over almost a two decade period (1998-2016) (Figure 1). Heart rate (HR) at the time of diagnosis was determined from the resting ECG rate or by heart rate recorded on initial examination. Naturally, this may introduce error since each patient in the study will not have HR assessed in a similar fashion as per protocol i.e. a set period of rest prior to recording heart rate. Sinus tacycardia was defined as a HR >100 per minute. LVEf measurements were taken at the time of PPCM diagnosis, at 6 months, then at 12 months afterwards. Baseline characteristics of the total cohort and those with a resting heart rate at diagnosis of > 100; >110; >120 per minute are shown in Table 1.
Figure 1. Flowchart of study sample inclusion and exclusion criteria
82 patients were included in the analysis and over 90% of women were diagnosed with PPCM post partum. A sizable number of women (41%) had their pregnancy complicated by hypertension or pre-eclampsia. At the time of PPCM diagnosis, 50 patients (61%) had a sinus tachycardia. Higher heart rates were associated with lower LVEf (Table 2).
Most women in this cohort (n=60) when initially diagnosed with PPCM, had severe LV dysfunction (LVEf <35%), of whom n=40 had an LVEf <25%. It is unclear from the data what proportion had bi-ventricular impairment or co-incident valvar regurgitation i.e. functional MR. Of note, almost all women included in this cohort were prescribed a loop diuretic (n=80) reflective of their heart failure symptomatic status. Most patients were treated according to guideline based medical therapy (beta blocker and ACE-I) with over a third prescribed spironolactone (n=32).
75% of patients had a full recovery of LVEf. Recovery of LV function was less likely to occur if the baseline LV impairment was lower. During follow up, 17 patients had at least one MACE (LVAD implant, cardiac transplant or death). Sinus tachycardia at diagnosis was associated with lesser chance of LV functional recovery (Table 3).
As one may expect, the majority of the women with MACE had baseline LVEf = <30% (n=14). Patients with LVEf <25% at baseline were 7x more likely to experience MACE. Six women required LVAD implant and 2 women required cardiac transplantation. A substantial number of women died (n=11, 13%) despite medical treatment for heart failure and it is unclear from the data presented what the causes of death were. It is unclear from the data which patients received an implantable defibrillator +/- CRT therapy.
This retrospective analysis suggests that sinus tachycardia in the pregnant woman, particularly a rate > 110 per minute, in the absence of other reversible causes, may be a ‘red flag’ finding. Resting heart rate alone is an imperfect measure and only 61% of patients with PPCM had a sinus tachycardia at diagnosis. However, a sinus tachycardia should stimulate focussed clinical assessment for signs of heart failure; possibly measure natriuretic peptide levels and to perform an echo to fully assess ventricular function.