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Re: Authors Response

Dear Editor,

We thank Dr. Ballo and colleagues for their interesting comments on our article. In agreement with our study, Ballo et al show a nonlinear association between circumferential midwall and longitudinal LV systolic function in patients with hypertension [1]. It is particularly noteworthy that this nonlinear association is apparent in two different study populations. The patients in our study were suffering from idiopathic heart failure (mean LVEF 44±17% and AVPD 6.9±2.7 mm) whereas the patients in Ballo´s study had a less severe diagnosis (arterial hypertension, mean LVEF 62 ±9.7% and AVPD 12.5±2.5 mm). Longitudinal function is dependent on subendocardial muscle fibres that are extremely sensitive to ischemia and increases in wall stress, and consequently capable of detecting small ventricular changes[2-4].

REFERENCES

[1] Ballo P, Quatrini I, Giacomin E, Motto A, Mondillo S.
Circumferential versus longitudinal systolic function in patients with hypertension: a nonlinear relation.
J Am Soc Echocardiogr. 2007;20:298-306.

[2] Nikitin NP, Loh PH, Silva R, et al.
Prognostic value of systolic mitral annular velocity measured with Doppler tissue imaging in patients with chronic heart failure caused by left ventricular systolic dysfunction.
Heart. 2006;92:775-9.

[3] Gruner Svealv B, Fritzon G, Andersson B.
Gender and age related differences in left ventricular function and geometry with focus on the long axis.
Eur J Echocardiogr. 2006;7:298-307.

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Re: Prognostic value of left ventricular long-axis versus short-axis systolic function in heart failure

Dear Editor,

Grüner Sveälv et al.(1) recently found that left ventricular (LV) long-axis atrioventricular plane displacement (AVPD) in heart failure (HF) patients was linearly correlated with short-axis fractional shortening (LVFS) in the lower range of AVPD, but not in the higher range of AVPD. They also observed that decreasing AVPD quartiles showed a stepwise association with worsening prognosis. Notably, a similar gradual association with outcome was less evident for LVFS, as no differences in outcome were found between the third and fourth LVFS quartiles.

These interesting results agree with our recent finding that the relation between longitudinal and circumferential systolic performance is nonlinear, as a depression in longitudinal indices such as AVPD and mitral annulus peak systolic velocity precedes that in endocardial or midwall circumferential function(2). Therefore, when plotting a long-axis versus a short-axis index (e.g., AVPD on the X-axis and LVFS on the Y-axis), the resulting relation tends to be horizontal in the higher range of indices, reflecting isolated long-axis impairment in the early stages of systolic dysfunction. Conversely, the slope of the relation rapidly increases in the lower range of indices, reflecting simultaneous deterioration in longitudinal and circumferential function in more advanced stages of HF. This explains the presence of linear correlation between AVPD and LVFS only in the lower range of AVPD.

Intriguingly, the more gradual association with prognosis observed for AVPD than LVFS may represent the clinical correlate of their nonlinear relation. Based on currently recommended cut-offs for normal LVFS (>25% in males and >27% in women)(3), most patients in the two highest LVFS quartiles (23-31% and >31%, respectively; overall, 72% males) had preserved short-axis function. These subjects fall in the horizontal portion of the AVPD-LVFS curve, where circumferential indices cannot identify patients at heightened risk due to subtle systolic dysfunction. In contrast, because longitudinal systolic impairment is an early and progressive event in the natural history of HF, and considering that it represents a powerful prognostic predictor in HF patients(4), decreasing AVPD values may be expected to reflect the effective stage of LV dysfunction and to parallel the corresponding increase in cardiovascular risk better than circumferential indices.

References

1. Grüner Sveälv N, Olofsson EL, Andersson B.
Ventricular long axis function is of major importance for long-term survival in heart failure patients.
Heart 2007 Jun 17; [Epub ahead of print].

2. Ballo P, Quatrini I, Giacomin E, Motto A, Mondillo S.
Circumferential versus longitudinal systolic function in subjects with hypertension: a nonlinear relation.
J Am Soc Echocardiogr 2007;20:298-306.

3. Recommendations for chamber quantification: a report from the American Society of Echocardiography's Guidelines and Standards Committee and the Chamber Quantification Writing Group, developed in conjunction with the European Association of Echocardiography, a branch of the European Society of Cardiology.
J Am Soc Echocardiogr 2005;18:1440-1463.