Relation Between New York Heart Association Functional Class and Objective Measures of Cardiopulmonary Exercise in Adults With Congenital Heart Disease.

Das BB, Young ML, Niu J, Mendoza LE, Chan KC, Roth T.
Am J Cardiol. 2019 Jun 1;123(11):1868-1873. doi: 10.1016/j.amjcard.2019.02.053. Epub 2019 Mar 15.

PMID: 30954207

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Take Home Points:

• NYHA class of patients is a simple measure for assessment of functional status, CPET remains an important tool to identify the source of exercise limitation in ACHD patients.
• CPET can provide objective and reproducible assessment of the cardiovascular, respiratory, and muscular systems.
• 3 of CPET parameters (pVO2, OUES, and maximum DP) overall correlate well with NYHA functional class especially between NYHA functional class I and III.
• If CPET cannot be performed, stratification using NYHA class is an acceptable alternative.

Commentary from Dr. Soha Romeih (Aswan, Egypt), section editor of ACHD Journal Watch:  Das et al compared the New York Heart Association (NYHA) functional class in adults with CHD patients with measured cardiopulmonary exercise testing parameters. This was a retrospective study which included 175 ACHD patients who underwent CPET between 2014 till 2018 in a single center. The majority of patients were repaired TOF (26%) followed by Fontan patients (19%) and repaired TGA with arterial or atrial switch (16%).

• The NYHA class was determined for each patient by physician assessment of patients’ self-reported symptoms before the exercise test or estimated from patient narrative from the medical record. Only patients with NYHA class I to III were enrolled in the study, as they were able to participate in CPET.
• Symptoms limited CPET was performed on all patients using treadmill according to modified Bruce protocol (97% of patients) or cycle ergometer ramping protocol (3% of patients). The measured parameters were:
  • Peak VO2 max, as the highest 30-second average during exercise.VO2 value was adjusted per ideal body weightthe normal was > 20 ml/kg/min.
  • The VE/VCO2 nadir was taken as the lowest 30-second average duringexercise, the cutoff of 34 (a prognostic tool of heart failure).
  • O2 uptake efficient slob (OUES) was measured as relationship between VO2 max and Log VE thought the exercise., cutoff value was 2,000.
  • Double product (DP) is the myocardial O2 uptake, defined as the amount of O@ consumed by the myocardium during exercise, was estimated by the product of heart rate and systolic blood pressure, cut off value was 20.000.

Results:

• Peak VO2in the overall study population was 26.4 ± 9.8 ml/kg/min or 72.7 ± 22.3% of predicted. There was a progressive decline in pVO2 with increasing severity of CHD (p = 0.001).

 

There was a strong negative correlation between functional class and pVO2, with a progressive decline from functional Class I to III (r = ¡0.48; p 0.0001). About ¼  of patients had pVO2 <20ml/kg/min and there was an overlap in pVO2 in each NYHA functional class.

 

However, 75% of NYHA class III had pVO2 <20 ml/kg/min compared with 10% in NYHA class I. Patients in functional class III had a markedly reduced pVO2 of 16.8 ± 4.5ml/kg/ min compared with 26.6 ± 6.1 ml/kg/min in class I (p = 0.0002).There was no significant difference in pVO2 between NYHA class II and III (p = 0.09), whereas the difference between NYHA class I and II and Class I and III are significant (p <0.004 and p <0.00002 respectively.

Figure 1. Relation between Peak VO2 and NYHA class. (A) Spearman correlation between pVO2 and NYHA class, (B) frequency of distribution of pVO2, (C) Relative distribution with a cut-off value of pVO2 20 ml/kg/min, and (D) Box and whisker-plot demonstrating median and quartiles of pVO2 by NYHA class. NYHA = New York Heart Association.

 

• The VE/VCO2 slope in the overall study population was 31.7 ± 5.4. Patients in functional class III had the higher VE/VCO2 slopes compared with class I and II, but there was no significant correlation between NYHA class and VE/VCO2 slope (r = 0.14, p = 0.37).

 

The distribution of VE/VCO2 slope was within upper normal limits in functional class I patients, but one-fifth of these asymptomatic patients (20%) had an abnormal slope > 34. Almost one half of patients in NYHA class II (42%) and III (50%) had a VE/VCO2 slope > 34.There was no significant difference between NYHA class I and II (p = 0.071), or between Class II and III (p = 0.263), whereas VE/VCO2 was significantly different between Class I and III (p = 0.011).

Figure 2 Relation between VE/VCO2 slope and NYHA class. (A) Spearman correlation between VE/VCO2 and NYHA class, (B) frequency of distribution of VE/VCO2, (C) Relative distribution with a cut-off value of VE/VCO2 34, and (D) Box and whisker-plot demonstrating median and quartiles of VE/VCO2 by NYHA class. NYHA = New York Heart Association.

 

• The VE/VCO2 slope in the overall study population was 31.7 ± 5.4. Patients in functional class III had the higher VE/VCO2 slopes compared with class I and II, but there was no significant correlation between NYHA class and VE/VCO2 slope (r = 0.14, p = 0.37).

 

The distribution of VE/VCO2 slope was within upper normal limits in functional class I patients, but one-fifth of these asymptomatic patients (20%) had an abnormal slope > 34. Almost one half of patients in NYHA class II (42%) and III (50%) had a VE/VCO2 slope > 34.There was no significant difference between NYHA class I and II (p = 0.071), or between Class II and III (p = 0.263), whereas VE/VCO2 was significantly different between Class I and III (p = 0.011).

 

 

Figure 2 Relation between VE/VCO2 slope and NYHA class. (A) Spearman correlation between VE/VCO2 and NYHA class, (B) frequency of distribution of VE/VCO2, (C) Relative distribution with a cut-off value of VE/VCO2 34, and (D) Box and whisker-plot demonstrating median and quartiles of VE/VCO2 by NYHA class. NYHA = New York Heart Association.

 

 

• The OUES in the overall study population was 2,565 ± 825. There was a progressive decline in OUES with increasing severity of NYHA class (r = ¡0.35, p <0.0001). Majority of ACHD patients had OUES > 2000. There was no significant difference in OUES between NYHA class II and III (p = 0.158), whereas the difference between NYHA class I and II and Class I and III were significant (p < 0.001).

Figure 3. Relation between OUES slope and NYHA class. (A) Spearman correlation between OUES and NYHA class, (B) frequency of distribution of OUES, (C) Relative distribution with a cut-off value of OUES 2,000, and (D) Box and whisker-plot demonstrating median and quartiles of OUES by NYHA class. NYHA = New York Heart Association; OUES = O2 uptake efficient slope.

• The maximum DPin the overall study population was 26,602 ± 6,127. There was a progressive decline in maximum DP with increasing NYHA functional class (r = ¡0.31, p <0.0001). Majority of patients had DP > 20,000.

 

There was no significant difference in maximum DP between NYHA class II and III (p = 0.749), whereas the difference between NYHA class I and II and Class I and III were significant (p <0.001 and p<0.05 respectively).

Figure 4. Relation between maximum double product and NYHA class. (A) Spearman correlation between double product (DP) and NYHA class, (B) frequency of distribution of DP, (C) Relative distribution with a cut-off value of DP 20,000, and (D) Box and whisker-plot demonstrating median and quartiles of DP by NYHA class. NYHA = New York Heart Association; OUES = O2 uptake efficient slope.

Conclusions:

NYHA functional class correlates with objective measures of CPET, however there is wide variability in measured exercise capacity in each NYHA classification. Therefore, whereas NYHA class of patients is a simple measure for assessment of functional status, CPET is an important tool to identify the source of exercise limitation in ACHD patients.