In the present study, LA volume assessed by echocardiography was strongly associated with future risk of MACCE (a composite of stroke, sudden death, and congestive heart failure) in HCM patients with normal pump function. However, LA diameter, a standard measure used to assess LA size, was not associated with the risk of MACCE. A previous study reported that HCM patients have a 4-6-fold increased risk of developing AF compared with the general population [5]. Furthermore, once AF has developed the risk of ischemic stroke may increase 8-fold in HCM patients relative to HCM patients with sinus rhythm, presumably via an increase in cardioembolic stroke [9]. In our study the risk of stroke was comparable between patients with chronic AF and PAF.
Outcome and LA volume
We previously reported that LA volume in sinus rhythm may be a strong predictor of future AF in patients with HCM [6]. Mild LA enlargement is common in HCM, and may be a consequence of impaired diastolic function associated with the thickened and noncompliant LV [10. 11]. Although assessment of LA enlargement appears to provide important information about the patients' outcome, unidimensional M-mode LA diameter cannot accurately measure LA size [12]. Similar to that previously described, our series indicated that LA volume was a better predictor of PAF and MACCE than was superior LA diameter [6, 13–15].
AF and stroke
LA dilatation promotes stasis of blood, which in turn predisposes to thrombus formation and the potential for embolization. In our study, LA size was associated with important risk factors for stroke and death. These observations underline the benefits of defining clinical markers able to non-invasively identify those patients with HCM who are at risk of developing PAF and suffering complication.
There are several factors that may influence outcome in patients with HCM and the occurrence of stroke and LA enlargement.
Indeed, in this study, Group A had a significantly greater number of patients with hypertension and PAF both of which may predispose to stroke and heart failure.
MR influences also in a relevant fashion LA volumes. In our study, Group A had a significantly greater number of patients with severe MR.
Echocardiography and risk for sudden death assessment
Using two-dimensional echocardiographic measurements, Spirito et al. showed that the risk of sudden death increased progressively in direct relation to wall thickness [3]. But, there were no significant differences of the distribution of hypertrophy between two groups in our study.
Previous paper showed that LV outflow tract obstruction is associated with an increased risk of sudden death [16]. Otherwise, Losi MA et al. showed that there was no statistical differences between patients with and without obstruction on outcome [7].
Clinically, HCM patients without obstruction were sometimes occurred complications. There were some clinical significances of echocardiographic parameters in patients with nonobstructive hypertrophic cardiomyopathy.
Study limitations
First, the method we used for detection of PAF based on clinical documentation with electrocardiographic confirmation may have underestimated the actual incidence of PAF. Some patients with AF may have been asymptomatic, and if they did not present to the hospital then the arrhythmia could have remained undetected. However, all patients presented at least once to our hospital within a 1-year period. 7 of 18 patients were in AF at the time they presented with a stroke. Second, we only measured the LA volume at baseline, not during follow-up. As the dilatation rate of LA volume may also be an important prognostic factor in patients with HCM. And in our study, we did not investigate the patients with LV outflow obstruction. Previous paper showed that LV outflow tract obstruction is associated with an increased risk of sudden death [16]. In this study, we excluded the patients with obstruction. We investigated whether LA volume predict adverse cardiac and cerebrovascular events in HCM patients, as exclusive for the influence of LV outflow tract obstruction. Finally, diastolic dysfunction is determined with deceleration time of LV inflow, occult systolic dysfunction detected with tissue Doppler analysis. We did not use tissue Doppler imaging in our study.
Nistri s et al. reported that body mass index and the ratio of early diastolic peak LV inflow velocity to peak myocardial early diastolic velocity (E/e') ratio affect LAV/BSA only in non-athletes. Many factors may influence LA volume [17].