In your code, you are computing the difference (time 1 - time 2), and then using that difference in proc TTEST. As you have suspected, this is not correct.
As noted by @tamhane, you can either (1) compute the difference and then test whether the difference is zero using proc UNIVARIATE using differences as the response variable, or (2) you can use pairs of values in proc TTEST with the PAIRED statement.
Each variable--MWT, LVEDD, EF and LA--will be analyzed separately.
For example, using TTEST with PAIRED using pairs of values
proc ttest data=hetal.es_pv;
paired MWT1*MWT2;
run;
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